Beginning April 1, 2013, the ALS Environmental laboratory in Winnipeg will begin the use of a new and improved analysis method for Petroleum Hydrocarbons in soils and other solids. The Microscale Solvent Extraction (MSE) Technique has been used successfully at other ALS Canada laboratories for almost five years and is now available at ALS Winnipeg as a CALA accredited test procedure.

The MSE method, also known as the “Tumbler” extraction technique, will be used for the analysis of CCME Petroleum Hydrocarbon fractions (F2-F4G) in soils, sediments, sludges, and wastes. The method has been demonstrated to meet all regulatory requirements specified by CCME and all provincial jurisdictions where ALS Canada operates.

What is the MSE Tumbler Technique

The MSE Tumbler technique employs a solvent extraction of a solid sample from within a sealed extraction vessel, using an end-over-end rotator. The process is based on US EPA Method 3570, Microscale Solvent Extraction. The end-overend rotational motion of the rotary extractor in combination with in-situ chemical desiccation provides exceptional soil dispersion, promoting maximum contact between dried soil particles and the extraction solvent. This provides a highly efficient extraction of petroleum hydrocarbons, even from complex sample matrices such as clays, peats, and sludges.

Regulatory Acceptance and Equivalency

The new method has been extensively tested for compliance with the CCME Petroleum Hydrocarbon Tier 1 method requirements.

ALS has conducted thorough validation and equivalence testing on this method using a variety of petroleum-contaminated samples and reference materials, with comparison against the CCME reference method (16-hour Soxhlet extraction). All CCME equivalence requirements were met, and all data quality objectives that form part of ALS Environmental’s quality management program were exceeded.

All ALS Canada laboratories that offer this method regularly demonstrate proficiency through comprehensive Quality Control practices, and by participation in CALA’s biannual Proficiency Test (PT) program.

New Standard Detection Limits

TThe new method employs slightly higher detection limits than have been used previously at ALS Winnipeg. Detection Limits (DLs) have been raised in response to client concerns about low level positive results due to the extraction of naturally occurring organic matter that is commonly found in many soil types. In all cases, our new DLs are more than five times below the lowest CCME Tier 1 guidelines.

The ALS MSE tumbler technique will provide our clients with reduced turn-around-times, and with improved precision and accuracy for CCME PHC tests.
Recovery of the relatively volatile F2 (C10-16) fraction is greatly improved with this method because evaporative losses are virtually eliminated with this technique.

Additionally, this method is less susceptible than the Soxhlet or Soxtec methods to false positive results in the F3 range, which can be caused by exhaustive extraction of natural organic material from soil types with very high organic carbon content (e.g. peat/muskeg, humic material, wood wastes, etc.).

Within the laboratory, the tumbler extraction technique minimizes solvent usage, health and safety issues, and the generation of wastes, which is consistent with the ALS program of pollution prevention and environmental stewardship. The plots shown at right summarize equivalence study data taken from five different ALS Canada laboratories, comparing results between the MSE Tumbler method and the Soxhlet reference method. The average relative percent differences (RPDs) between the two methods were less than 2% for all three hydrocarbon fractions (F2, F3, F4).

Implementation Schedule

Beginning April 1, 2013, ALS Winnipeg will utilize MSE Tumbler extraction as the primary test method for the analysis of CCME F2-F4G parameters in solids. We will continue to offer our Soxtec method by special request. For further information please contact ALS Environmental at 204-255-9720 or toll free 1-800-668-9878.

www.alsglobal.com

As a class of organic compounds, PAHs are characterized by bonded aromatic rings that do not typically carry other functional groups or branched groups substituted for hydrogen atoms. PAHs occur in fossil fuel materials such as oil, coal, tar and fuels. They are produced as a result of fuel burning. They are also found in products such as burned tobacco, incense, and some plant-based oils. To further understand the sources of PAHs, they may be classified as follows:

• Petrogenic – These are PAHs derived from petroleum inputs and generally associated with fossil fuels.
• Pyrogenic – These are PAHs which are derived from combustion sources.
• Biogenic – These are PAHs formed from natural biological processes.

The toxicity of PAHs is dependent upon the structure or arrangement of aromatic rings. For example, the toxicity of some PAH isomers (with the same formula and number of rings) can vary from being effectively nontoxic to being very toxic. The more toxic or carcinogenic PAHs may be small or large. The USEPA has identified seven PAH compounds as probable human carcinogens.

PAHs are lipophilic, meaning they will dissolve more easily in fats, oils, and lipids than in water, leading to a greater accumulation in a wide variety of organisms and animals, including humans. Due to the toxic nature of several of the more common PAHs, this accumulation can in turn lead to carcinogenic or mutagenic effects. Other negative health effects have been identified and studied, as well. Bioaccumulation of PAHs in marine organisms, such as  edible shellfish, is commonly studied due to their pathways to humans. The effects of high prenatal and childhood exposure in humans are being studied as well.

Applications and Data Uses

In environmental testing, the analysis of samples for PAHs was included in some of the earliest analytical protocols and methods. Early EPA methods focused on 16 common PAHs, which were  listed by the EPA as “priority pollutants” with analyses performed using GC/FID, GC/MS, and HPLC/UV for environmental monitoring and cleanup. The 16-compound list was often expanded to include 2-methylnaphthalene and dibenzofuran. As the need to assess a broader group of PAHs and related compounds increased, additional analytical alternatives were developed.

Prior to the last decade, analyses targeting a broader group of PAHs and related compounds were usually restricted to research efforts and major environmental disasters, in which new analytical alternatives were developed. Although PAH analysis is still used for environmental monitoring and cleanup, it is now commonly used for forensic/fingerprinting investigations, damage assessment from petroleum products and spills, studying pyrogenic mechanisms, the determination of biogenic vs. non-biogenic sources, and studying the environmental effects of alkylated PAHs.

Advances in instrumentation and the use of GC/MS–Selected Ion Monitoring (GC/MS-SIM) has resulted in much lower detection and quantitation levels, as well as the development of methods specifically targeting PAHs and alkylated PAHs for specific data evaluations. Many laboratories have established these specialized tests, which can provide detection and quantitation limits up to 100 times lower than common full-scan GC/MS analysis.

The study of environmental disasters related to petrogenic PAHs has led to the inclusion of additional PAHs and alkylated PAHs as routine target analytes in many environmental analyses. Alkylated PAHs are normal PAH structures, but have at least one hydrogen atom substituted with an alkyl group. These “extended” PAH and alkylated PAH analyses are commonly used to perform fingerprint analyses for forensic purposes. For example, the petroleum-related alkylated PAHs, such as alkylated naphthalenes, alkylated phenanthrenes, alkylated dibenzothiophenes, alkylated fluorenes, alkylated chrysenes, and certain unsubstituted PAHs, are much more significant components in crude oil compared to many of the priority pollutant PAHs.

Additionally, considering that oils and refined petroleum products from separate sources generally have differing relative amounts of PAHs, combined with alteration to normal distributions due to weathering, the ability to analyze a broad range of compounds becomes essential.

The analysis of pyrogenic PAHs, those generated in combustion of organic materials, is often used in the study of PAH formation mechanisms under various combustion conditions, including incomplete combustion. With pyrogenic materials the contribution of unsubstituted PAHs is much higher than the related alkylated homologue. Also, there is a more skewed distribution of alkylated PAHs in pyrogenic PAHs as compared to unweathered petrogenic alkylated PAHs. The data from extended PAH and alkylated PAH analyses can be evaluated to determine the sources of the present PAHs. In both petrogenic or pyrogenic studies, the ratio of PAHs is commonly used to identify sources of contaminant PAHs.

Expanding the PAH analytical techniques to include the determination of compounds indicative of biogenic PAHs, such as retene and perylene, can be used to determine the relative contribution or source of naturally occurring biogenic PAHs. These data can be used to distinguish biogenic sources of PAHs from petrogenic or pyrogenic sources. Examples of other analytes being studied, but not classically included in PAH analyses, are as follows:

• Biphenyl – An unsubstituted, 2-ring PAH that can be used for characterization and identification petrogenic sources.
• Carbazole – A nitrogen-containing PAH that is produced from coal tar and crude oil with several industrial uses. It is a suspected carcinogen with potential metabolic pathways identified.
• cis/trans-Decalin and alkylated decalins – Decalin is a bicyclic compound and is the saturated analog (C10H18) of naphthalene. Decalin is an industrial solvent.
• Dibenzofuran – An oxygen-containing PAH (two benzene rings fused to one oxygen-containing ring in the middle). It is present in low-% levels in creosote and commercial coal tars. It has been listed by the USEPA as a volatile hazardous air pollutant of potential concern and it a targeted analyte under EPA CERCLA and SARA (Superfund).
• Benzothiophene and alkylated benzothiophenes – Sulfur-containing PAHs that can be used for characterization and identification petrogenic sources. Benzothiophenes occur naturally in petroleum-related deposits.
• Dibenzothiophene and alkylated dibenzothiophenes – Similar to benzothiophene, dibenzothiophene is a sulfur-containing PAH, with two benzene rings fused to a thiophene ring. Alkylated dibenzothiophenes occur in heavier fractions of petroleum.
• Naphthobenzothiophene and alkylated naphthobenzothiophenes – Similar to dibenzothiophene but with a naphthyl group substituted for one of the benzene rings.

With the advancement in analysis technology and capability from a standard 16-compound analysis by GC-FID, GC/MS, or HPLC to today’s low-level GC/MS-SIM analyses that include greatly expanded compound lists, researchers, engineers, risk assessors, toxicologists, and other data users are using the analysis to study PAHs and sources extensively. This is evident in the examination of extended PAHs compounds list by the NOAA National Status and Trends program (NOAA NS&T), state programs (such as Washington Department of Ecology), and disaster assessment. The following table provides a comprehensive list of PAHs and related compounds discussed in this paper and of current interest.

PAHs, Alkylated PAHs, and Related Compounds of Environmental Interest

Gypsum is often applied as an amendment to soils that exhibit a high sodium adsorption ratio (SAR).  The addition of gypsum can reduce a soil’s clay plasticity, thus improving drainage and ease of cultivation. Estimating the correct amount of gypsum required to remediate a particular site is an inexact science requiring experience and consideration of specific site history and conditions, but models described in the literature can produce theoretical estimates to provide guidance.  As a service to our clients, ALS now offers two theoretical calculations for gypsum requirement that are suited to two common categories of salt-impacted soil on the Canadian prairies.

• Natural salt contamination – Sodic soils (e.g. solonetzic soils) contain naturally occurring sodium salts. After centuries of accumulation, sodium occupies a substantial percentage of the soil’s cation exchange capacity (CEC).
• Man-made salt contamination – Spills of produced water (brine, sodium chloride) in the oil industry immediately increase the electrical conductivity (E.C.) of the soil solution, damaging seeds and hindering root uptake of water by growing plants. A secondary effect of brine spills is to increase soil SAR, thus affecting clay properties as already described.

Calcium amendments – Usually, calcium and magnesium ions predominate in soils, so that the SAR of a saturated paste extract is normally very low. Calcium-containing compounds can be used to bring high SAR values back below detrimental levels.  Soluble salts such as calcium nitrate (“Envirofloc”) and concentrated calcium nitrate solutions supplied in drums are fast-acting, but carry the risk of damage to growing plants due to high E.C. In contrast, insoluble calcium carbonate may have no immediate effect on SAR. Gypsum (calcium sulphate) has limited solubility causing only a modest E.C. increase, making it a widespread choice in SAR remediation.

Suitable rates of gypsum application – Rates of application range from a few tonnes per hectare up to as much as 50 t/ha. Due to its limited solubility, gypsum should be worked into the surface. Since soil cultivation depth is often approximately 15 cm, recommended rates are normally given in tonnes per hectare for a layer of soil 15 cm deep.

In estimating the theoretical gypsum requirement (TGR), it is important to distinguish man-made salinity – where the objective is to supply enough calcium to bring the SAR of the soil solution down to non-damaging levels – from natural salinity, where the need is to displace exchangeable sodium from the soil’s cation exchange complex.

Method 1: TGR for Brine-Contaminated soils (TGRbrine) – In this approach, an amount of gypsum is calculated that would supply enough soluble calcium to lower the soil’s SAR from its current, high value to a target saturated paste value considered non-damaging to soil structure.

TGRbrine (tonnes per hectare-15 cm) = 0.335 a²{(1/b²) – (1/c²)} x (% sat./100)   . . .   [1]

Where:
a = sodium ion concentration in saturated paste extract (meq/L),
b = the target SAR after soil remediation (ALS uses 7),
c = the current on-site SAR,
and % sat. = mL of water required to saturate 100 g of dry soil

Any exchangeable Na on the soil’s cation exchange complex is ignored. While some displacement of Ca and Mg cations by Na occurs after a salt spill, it is usually minor compared with Na in solution.

• TGRbrine increases with electrical conductivity E.C. (due to increased sodium concentration) and also with increasing site SAR.
• If the SAR is already below 7, the TGRbrine becomes negative and is set to zero.
• Equation [1] can give very high TGR values; if TGRbrine exceeds 50 t/ha, a default rate of 50 t/ha is recommended. In such cases, the client will need to re-visit the site later to assess progress.
• On brine-contaminated sites with high E.C., gypsum treatment is usually not a cure in itself; salts often need to be physically removed, by diverting saline pore water into trenches, bell-holes or tile drains, followed by safe (e.g. deep well) disposal.

Method 2: TGR for Naturally Sodic Soils (TGRsodic) – In this approach, an amount of gypsum is calculated that would supply enough exchangeable calcium to lower the soil’s exchangeable sodium percentage (ESP) from its current, high value to a target value considered non-detrimental to soil structure. Empirical allowance is made for incomplete displacement of Na by Ca.

TGRsodic (tonnes per hectare-15 cm) = 0.021 x CEC x (I – F)                        . . .  [2]

Where:
CEC = the soil’s cation exchange capacity in cmol(+)/kg  [= meq/100 g],
I = the initial, existing ESP value,
and F = the final, target ESP (ALS uses 8%, corresponding to an SAR of ~ 7)

Any sodium in the soil solution is neglected, since it is minor compared with the amount of exchangeable sodium naturally present on the cation exchange complex of sodic soil.

• CEC can be estimated from % sat. because both parameters are governed by the amounts of clay and organic matter in the soil (USDA 1954).
• For sodic soils, the initial ESP can be estimated from the SAR (USDA 1954).
• TGRsodic increases with increasing SAR, but is unaffected by soil E.C.
• If the SAR is already below 7 the calculated ESP is below 8, so that TGRsodic becomes negative and is set to zero.
• TGR calculated by eqn. [2] is usually well below its theoretical maximum of approximately 50 t/ha.

Conclusions: – TGR values obtained by the above methods can differ considerably (see examples below). It is important, therefore, to use the approach that is appropriate to the chemistry and history of a particular site, and also to recognize that gypsum amendments alone are not always sufficient or practical for the remediation of all salt-impacted sites.

TGR values should always be interpreted as estimates. Calculated TGR values are best regarded as an index of salt contamination and of progress towards site remediation, rather than as a definitive application rate. TGR values cannot be as accurately predicted as, for example, fertilizer recommendations for a crop planted on a field tested for available nutrients. However, TGR values are useful in keeping application rates consistent, either from one site to another or from one application date to the next.

TGR is normally reported as tonnes per hectare (t/ha) to a treatment depth of 15 cm.  To convert to kg of gypsum per cubic metre of soil, multiply by 0.67. To convert to units of tons per acre at the same treatment depth, multiply  by 0.45.

References:

Ashworth et al. 1999. Canadian Journal of Soil Science 79: 449-455.

Oster and Frenkel 1980. Soil Sci. Soc. Amer. J. 44: 41-45.

U.S. Department of Agriculture. Handbook No. 60, 1954 (available on-line).

The synthetic production of ammonia by the Haber-Bosch process has been called the most important invention of the 20th century. Fritz Haber received the Nobel prize in 1919 for pioneering the “fixation” of nitrogen, where nitrogen gas is converted to ammonia, a reactive form of nitrogen that can easily be taken up by plants. Nitrogen from synthetic fertilizers now provides more than half of the nutrients required by the world’s crops. Without the ammonia produced from the Haber-Bosch process, our planet could not feed seven billion people.

Ammonia plays a key role in the global nitrogen cycle, and is produced naturally through the decomposition of nitrogen-rich organic matter. However, it is also a very common environmental pollutant, and in 1990 was listed as the top priority on Environment Canada’s Canadian Chemical Spill Priority List. Outside the fertilizer industry, anthropogenic point sources of ammonia include the textile industry, household chemicals, explosives, the plastics industry, oil refineries, iron and steel mills, meat processing plants, and sewage treatment plants.

At low levels, ammonia in drinking water is not considered toxic to humans. It is produced naturally in the human body, and is efficiently targeted and detoxified by specific enzymes. However, ammonia is highly toxic to fish and amphibians at very low concentrations, since they lack these enzymes.

A Canadian Water Quality Guideline for the Protection of Freshwater Aquatic Life has been established for ammonia at 0.019 mg/L (CCME 2010; http://ceqg-rcqe.ccme.ca/download/en/141/). It is important to consider that this guideline applies only to un-ionized ammonia (NH3). Ionized ammonia (ammonium, NH4+) is much less toxic to aquatic life.

To understand this guideline, one must understand that the NH3 and NH4+ species co-exist in aqueous solution in an acid/base equilibrium that is controlled primarily by pH, and to a lesser extent by temperature (see chart). Ammonium (NH4+) is the principal species that exists under the pH and temperature conditions of most natural waters. The proportion of un-ionized ammonia, which exists in water as a dissolved gas, increases as the pH becomes more basic and as temperatures rise. Equations within the CCME guideline document permit the calculation of the fractions of NH3 and NH4+ that will exist in any water sample as a function of pH and temperature.

Water samples to be tested for ammonia should be preserved with H2SO4 immediately after collection in either glass or plastic bottles. Under acidic conditions, ammonia exists entirely as the ionic ammonium species, which is relatively stable when stored under refrigeration (recommended hold time limit is 28 days).

By convention, laboratory test results for ammonia are almost always reported as “Ammonia (as N)”, which refers to the sum of the un-ionized (NH3) and ionized (NH4+) ammonia species in the sample, expressed in units of milligrams of nitrogen per litre of sample.

To compare laboratory test results with the CCME water quality guideline, one needs to convert Ammonia (as N) results into the corresponding concentration of un-ionized ammonia in the water body (in mg/L of NH3), using the CCME equations and the field pH and temperature measurements (see examples that follow). Upon request, ALS can compute and report un-ionized ammonia concentrations if field pH and temperature are provided. Alternatively, one may compare “Ammonia (as N)” results against a table within the CCME guideline document that lists computed water quality guidelines for “Total Ammonia” (i.e. ionized plus un-ionized ammonia) at specified temperature and pH values. However, the values listed are “as NH3″ instead of “as N” (multiply by 0.8224 to convert to “as N”), and are only provided in 5°C temperature increments and 0.5 pH unit increments.

Molecular Weight of Nitrogen (N) 14.01
Molecular Weight of Ammonia (NH3) 17.03
Molecular Weight of Ammonium (NH4) 18.04

Ammonia in Your Aquarium

Anyone who has kept pet fish should know that an imbalance in the nitrogen cycle is the most common cause of fish mortality in aquariums. Ammonia is produced rapidly in aquariums by the degradation of nitrogen-containing organic matter (fish waste and uneaten food). Healthy, established aquariums contain at least two bacterial strains that work together in a 2-step process to eliminate ammonia. Nitrosomonas bacteria first oxidize ammonia into nitrite (NO2), which is also highly toxic to fish. In the 2nd step, Nitrobacter bacteria convert nitrite into nitrate (NO3), which is tolerated by fish at much higher levels. Toxic levels of ammonia often build up quickly in newly established aquariums that don’t have established colonies of these two necessary bacterial strains, which is why fish often die in new aquariums. A common mistake people often make is to change out all the water on an established aquarium during tank cleanings – this can upset the balance of the nitrogen cycle, causing ammonia to accumulate, which could mean trouble for your fish.

Keep the Nitrogen cycle in balance in your aquarium to minimize Ammonia buildup!
(photo: Sujit Kumar & Dieter Karner)

For more information, visit http://www.alsglobal.com/environmental/services/north-america-environmental-services.aspx .

Currently, the Environmental Protection Agency (EPA) monitors public drinking water at a maximum contaminant level (MCL) of 0.006 mg/L for DEHP. The FDA will match this level for bottled water beginning April 16. The decision to regulate DEHP levels was made following the 2010 comment period regarding the 1993 proposal for increased bottled water management.

The FDA is adopting EPA-approved analytical methods for contamination detection. Any bottled water that exceeds the allowable level of DEHP, following analyses using these approved methods, will be labeled misbranded under section 403(h)(1) of the Federal Food, Drug and Cosmetic Act (FD&C Act). This misbranding will be fact in all cases that do not present a statement of substandard quality.

Read the full Federal Register notice at http://www.gpo.gov/fdsys/pkg/FR-2011-10-19/pdf/2011-26707.pdf

Vapor intrusion is a fate and transport process characterized by the upward movement of volatile chemicals from subsurface contamination (e.g., buried waste, contaminated groundwater) into overlying buildings. The potential for adverse human health effects from exposure to indoor air vapors has motivated private, state, and federal entities to develop guidance documents and protocols specific to the collection and analysis of soil vapor data.

Figure 1: Generalized schematic of the pathway for subsurface vapor intrusion into indoor air.

While the sample collection methodologies have improved over time, specifics related to laboratory quality control and data validation have not been comprehensively addressed. The United States Environmental Protection Agency (USEPA) Contract Laboratory Program National Functional Guidelines (NFG) for Organic and Inorganic Data Review (USEPA 2008 and 2010) were developed to provide practitioners consistency and accountability when evaluating and reviewing laboratory analytical data produced from soil and water samples. However, the USEPA has not yet published guidelines specific to the evaluation of soil vapor data. Documenting the validity of soil vapor data is a key component of conducting any vapor intrusion pathway assessment since many of these studies are conducted to support human health risk assessment. In the absence of applicable guidance, Trihydro Corporation has developed best practices from experience in field collection of soil vapor samples, validation of the resulting data, and careful study of soil vapor analytical methods.

The key components of these best practices are sample planning, sampling technique, laboratory analysis, and validation of the resulting analytical data. The following sections provide the components of this best practice approach.

Sample Planning

Sampling equipment cleanliness plays a crucial role in soil vapor sampling and data quality analysis. Since canisters and associated equipment (e.g., flow controllers, vacuum gauges, etc.) are reused, equipment cleaning and certification are essential to obtaining good data quality. If equipment is not properly cleaned, artifacts can remain in the equipment, resulting in a high bias. This phenomenon was quantitatively explored in a paper by Fortune, et. al. (2008). Laboratory experiments confirmed that when flow controllers and/or vacuum gauges were reused without adequate cleaning, carryover from high concentration samples resulted in false positives over the laboratory reporting limits.

After a soil vapor sample has been analyzed in the laboratory, the canister is subjected to a cleaning process using cycles of heat, humidification, and flushing with a clean gas source (nitrogen or air). Canisters are cleaned on a manifold in small batches of up to twenty. Flow controllers, vacuum gauges, and other components of the sampling train are often cleaned in a similar manner. To measure the effectiveness of the cleaning process, the equipment is analyzed for the compounds of interest. To achieve a clean certification, all compounds of interest should be below the laboratory detection limits.

Canisters and associated equipment may be either batch or individually (100%) certified as clean. Both options are compliant with Method TO-15; choosing which option to use will depend on the data quality objectives of the sampling program.

• Batch Certification – One canister per cleaning batch is deemed representative of all canisters in the batch and analyzed for the compounds of interest. Many laboratories will further employ the best practice of certifying the canister that displayed the highest concentrations in its previous use. If the chosen canister passes certification, the entire batch is certified as clean. The consequence of batch certification is that the data user does not have complete certainty that each canister was clean before use in the field.
• 100% Certification – Each canister is analyzed for the compounds of interest. Flow controllers, vacuum gauges, and other components of the sampling train may be certified in a similar manner. When using 100% certified canisters, it is important that the certified pieces (canister, flow controller and vacuum gauge) be used together and not mixed with other certified units. While significantly more labor intensive (and therefore more costly), this option gives the data user confidence that every piece of equipment used was certified as clean prior to sampling. Individual certification is often recommended at sites with sensitive receptors (e.g., schools, daycare facilities) and for sampling programs that may be involved in litigation.

Compounds likely to exhibit carryover in sampling equipment include toluene, tetrachloroethene, trimethylbenzenes, naphthalene, and other similar VOCs with molecular weights over approximately 160 g/mol and/or boiling points over approximately 160-170°C. Lighter molecular weight/boiling point compounds are usually more easily removed during the cleaning process. Excessively high concentrations (greater than approximately 100,000 μg/m3) of any compound may also have a tendency for carryover; therefore, equipment exposed to these concentrations may require additional cleaning.

Equipment may also be segregated by use and concentration level in the laboratory to reduce potential residual carryover in the sampling equipment and/or analytical system when low reporting limits are needed. For example, canisters used for ambient air and indoor sampling, which typically require low-level reporting limits, could be segregated from canisters used for sampling soil gas, which tend to have higher levels of contaminants.

Sampling Technique

Field processes can greatly impact the quality of sample data. To collect representative soil vapor samples, it is important to limit leakage across the sample train, which can consist of the vapor probe, flow controller, nylon plastic tubing, compression fittings, ball valves, and the sample canister. It is also important that any components used in the sampling train be evaluated to determine if they have the potential to cross contaminate the sample. The following quality control measures can be implemented when collecting soil vapor samples to improve data quality.

Canister and Sample Train Leaks

Canister and sample train leaks can allow ambient air to enter the sampling system, resulting in the collection and analysis of non-representative samples. Common causes of leaks include worn or faulty valves and fittings, over-tightened fittings, improperly installed vapor probes, and broken or cracked tubing.

Valves and connection fittings will wear over time. If a valve or fitting is used for more than one sample, it should be thoroughly decontaminated and inspected for wear. The threads should be intact, and valves should close completely. Stainless steel medical grade valves and fittings are recommended since they are harder than brass and tend to be more durable. Fittings should be snug, but not over tightened. Over tightening fittings will cause damage to the threads and can also result in crimping of the tubing. Crimping may create a gap in the connection, allowing ambient air to enter the system. Furthermore, nut and ferrule components should also be comprised of stainless steel, as plastic components are more susceptible to warping during tightening, allowing gaps in the connection.

Nylon plastic tubing, which is commonly used for vapor sample collection, is moderately flexible and usually works well with the typical nut and ferrule fittings. Tubing should be used only once to prevent cross contamination. Nylon plastic tubing becomes brittle in cold weather and may crack or break. In order to avoid cracking and breaking, tubing should be inspected prior to connecting to the sample train, and sections should be cut to lengths that will accommodate bending and placement of the sample train components.

Proper installation of a vapor probe, whether a sub-slab or soil vapor sampling point, is critical to collecting high-quality samples. Sub-slab vapor probes should be properly sealed to the surface of the slab using a non-volatile material such as quick-setting hydrated cement. The seal around the vapor probe should be allowed to dry thoroughly prior to attaching components of the sample train. Soil vapor probes should be installed and sealed using impermeable barriers such as bentonite. For nested soil vapor wells, a seal test should be conducted by applying a vacuum to a vapor probe while monitoring the next deeper or shallower probe with a vacuum gauge. A measurable pressure change may indicate an improper seal and require abandoning the sampling point.

Canister Pressure Monitoring

Canisters are prepared in the laboratory and are typically shipped to sampling locations with a pressure as close to 30.0 inches of mercury (inHg) as possible, depending on the laboratory’s elevation. Atmospheric pressure can range from 29.2 inHg at sea level to 24.9 inHg at 5000 feet. Once a canister is received at the sampling location, the canister pressure should be measured by the sampling team and compared to the laboratory measurement recorded on the receiving documents. Field and laboratory canister pressure readings should be consistent, accounting for differences in pressure due to the change in elevation from the laboratory to the sampling site, and differences in the gauge between the laboratory and the field. The MassDEP APH Method suggests an acceptable difference of plus or minus 5 inHg (MassDEP 2010). However a site specific value could be determined. Use of a digital gauge is recommended over the gauges provided by the laboratory, as the laboratory gauges tend to be less accurate due to wear and tear during shipment. Canisters exhibiting an excessive loss of vacuum from the laboratory to the sampling location should be considered to have leaked in transport and should not be used for sampling.

In addition to monitoring the canister pressure from the laboratory to the sampling location, the pressure should be monitored and recorded after sampling and prior to transport to the laboratory. The laboratory will measure the pressure again upon receipt and report this reading along with the sample results. A residual vacuum should remain in the canister after sampling. This residual vacuum allows the data user to determine if canister leaks have occurred during shipment from the site to the laboratory following sample collection. Canisters exhibiting an excessive loss of vacuum from the sampling location to the laboratory to the sampling location should be considered to have leaked in transport, and the resulting data should be rejected.

Shut-In Testing

Shut-in testing is a technique used in the field to evaluate the integrity of the sample train. A typical shut-in test involves closing the valve to the vapor probe and evacuating the lines to a measured vacuum. Then, the vacuum is shut by closing the valve at the opposite end of the sampling train. This vacuum is monitored using an in-line vacuum gauge. The initial measured vacuum should be maintained for 30 seconds for a positive shut-in test. If the vacuum dissipates from the sample train, the shut-in test has failed, and all connections should be inspected for leaks.

Purging and Tracer Testing

Purging, along with the use of a tracer compound, is performed to remove ambient air from the vapor probe and tubing and to check for leaks in the sample train. Tracer compounds can include gaseous materials such as helium and 1,1 diflouroethane (duster spray) and liquid compounds such as isopropyl alcohol, pentane, and Freons. During purging, the sample train is shrouded, and a tracer compound is applied within the shroud. Soil vapor is then purged from the vapor point into a Tedlar bag, where it can be monitored using field instruments.

There are advantages and disadvantages to all tracer compounds (ITRC 2007). Selection of a tracer is specific to the project needs but should include consideration of:

• Accessibility of the tracer
• Toxicity
• Interference with analytical results
• Real-time monitoring
• Quantitative evaluation of leakage

Since liquid tracer compounds are typically measured in the laboratory (after sampling is complete), the use of helium is prevalent in the field because it can be monitored using a hand-held helium detector. Helium is non toxic and can be purchased from gas suppliers. Ultra high purity grade helium should be used to limit the potential for VOC cross contamination that can occur with party-grade helium. Real-time monitoring of helium in the field allows the sampler to determine if the tracer gas has infiltrated the sample train. The concentration of helium measured in the Tedlar bag should read less than 5% of the average shroud concentration. If the helium measurement is greater than 5% of the average shroud concentration, the sample train should be inspected for leaks and retested. Should leakage occur in the field, the percent can be quantified using the laboratory results along with the known shroud concentrations measured in the field during sample collection. This allows the data user to determine if the leak was significant enough to warrant the data unusable. Other tracers that do not allow for field measurement can only be qualitatively evaluated, thereby resulting in less defensible data.

Additionally, the use of helium as a tracer is recommended since its presence will not interfere analytically with the Method TO-15 VOC analysis. For example (as discussed in ITRC 2007), if the sampling system had a 0.1% leak (i.e., below 5%, and considered acceptable by any regulatory agency) and isopropyl alcohol was used as a tracer, the resulting concentration of isopropyl alcohol in the Method TO-15 sample (making conservative assumptions) would be over 14,000 μg/m3. This tracer concentration would force the lab to perform a dilution on the sample, thus raising reporting limits of all target VOCs.

Laboratory Analysis

When choosing a volatile organic compounds (VOC) analytical method for soil vapor sample analysis, a few common options exist: USEPA Method TO-15, which utilizes gas chromatography/mass spectrometry (GC/MS) and was originally written for ambient air samples; and USEPA Test Methods for Evaluating Solid Waste, Physical/Chemical Methods (also known as SW846) Method 8260B, which utilizes GC/MS and is widely used for groundwater and solid waste samples.

While Method 8260B technically allows for analysis of vapor phase samples (“air” is mentioned in Section 1.2), the method does not precisely define a procedure for vapor phase sample introduction and/or calibration considerations with typical 8260B purge and trap analytical equipment; therefore, analytical procedures must be significantly modified by the laboratory to accommodate vapor phase samples. Because of this ambiguity, there is no unified approach among laboratories for introducing soil vapor into the analytical system (Tuday 2008). Adding to the inconsistency, state certifying agencies do not typically certify laboratories (fixed or mobile) specifically for soil vapor analysis via 8260B. Potential losses of vapor phase samples in the analytical system should be monitored via additional quality control such as a vapor phase check standard. This protocol (called a tertiary standard) has been adopted by the Arizona Department of Environmental Quality (ADEQ 2009). The tertiary standard is comprised of a third source vapor standard and is used to verify the recovery of the vapor standard compared to the purged aqueous standard. Additional quality control is performed on the purge liquid (e.g., surrogates, internal standards, matrix spikes, etc.); this additional tertiary standard, if performed, is the only quality control directly relevant to the vapor phase.

Method TO-15 is a standardized method specific to the vapor phase. Although Method 8260B can successfully be used as an investigative tool for certain applications (if performed with the appropriate sample introduction and quality control), Method TO-15 is preferred when soil vapor data are intended for use in support human health risk assessments. Various laboratory accreditation authorities routinely audit and certify laboratories for this method, helping to ensure inter-laboratory consistency. All quality control parameters in Method TO-15 are specific to the vapor phase (calibration standards are in the vapor phase, control samples and method blanks are in the vapor phase, etc.).

Other canister-based USEPA methods are occasionally referenced in guidance documents, quality assurance project plans (QAPPs), and/or work plans. USEPA Method TO-14 was originally published in March 1989 in the Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air. In January 1999, Method TO-14 was revised and updated as Method TO-14A in the Second Edition of the Compendium of Methods; as such, Method TO-14 has been superseded by Method TO-14A. Method TO-15 was a new method added to the Second Edition of the Compendium in January 1999. Method TO-15 is larger in scope and better defined for the analysis of VOCs in air and other gaseous matrices than Method TO-14A. In practice, Method TO-15 has supplanted Method TO-14A as the preferred method for the analysis of VOCs in air.

Method TO-15 can be used to quantify a subset of individual VOCs, typically from C₃ to C₁₂. A vapor phase calibration standard is analyzed for each compound of interest, and an internal standard calibration technique is used. Although originally written for ambient air, Method TO-15 can be applied to the soil vapor matrix. Since no specific compound list is specified in the method, the compound list of VOCs may vary from laboratory to laboratory; however, most laboratories will report concentrations of common VOCs such as benzene, toluene, ethylbenzene, xylenes, tetrachloroethene, trichloroethene, and other chlorinated solvents.

When analyzing a sample via Method TO-15, the data user may request that the laboratory also perform (on the same sample) an analysis of “Tentatively Identified Compounds (TIC).” The TIC analysis will identify and/or give an estimated concentration for any compound present that is not otherwise reported in the Method TO-15 analysis. Since adding the TIC analysis will give a more complete list of VOCs in the sample, this additional step is often useful if the full characterization of a site is unknown.

For petroleum hydrocarbon sites, analyzing a canister sample via the Massachusetts Department of Environmental Protection (MassDEP) Air-Phase Petroleum Hydrocarbon (APH) Method (MassDEP 2010) may be useful. This method, based on Method TO-15, reports target VOCs associated with petroleum products, but it also reports aliphatic and aromatic hydrocarbon fractions (C₅-C₈ aliphatic hydrocarbons, C₉-C₁₂ aliphatic hydrocarbons, C₉-C₁₀ aromatic hydrocarbons) for risk assessment purposes. Non petroleum-related compounds that fall between the retention time markers of a hydrocarbon range (e.g., d-limonene, a common essential oil found in household cleaners, within the C₉-C₁₂ aliphatic range) may be subtracted per the data user’s request. The results will render a more accurate representation of the compounds related to petroleum product. While other similar fractionated approaches exist for soil and groundwater analyses in other states (e.g., the Northwest Total Petroleum Hydrocarbons (NWTPH) methods), the Massachusetts APH Method is the only one of its kind to specifically address petroleum product in the vapor phase. Both Method TO-15 and the Massachusetts APH Method can be performed on the same canister sample.

Other laboratory analyses that may be performed on soil vapor samples include an analysis for a leak test tracer (e.g., helium) and an analysis for permanent gases associated with aerobic biodegradation (methane, carbon dioxide, oxygen) via USEPA Method 3C or American Society for Testing and Materials (ASTM) Method D1946. In most cases, all of the analyses may be performed out of the same canister. In some cases, a separate canister or Tedlar bag sample may be required; the data user should coordinate in advance with the analytical laboratory.

Data Validation

Analytical data quality is an important aspect of environmental investigations. Understanding the different components that may affect data quality can provide a greater understanding of the results and the possible shortfalls of the data. The USEPA Contract Laboratory Program NFGs for Superfund Organic Methods Data Review provides guidance for validating analytical data quality; however, this specific guidance includes data produced from solid and water matrices and methods specifically applicable to those matrices. Analytical air methods, such as Method TO-15, document sampling and analytical procedures for the measurement of some VOCs and some hazardous air pollutants; however, the methods provide procedures under conditions typical of those encountered in routine ambient air analysis. The methods do not account for all possible conditions. Therefore, data validation best practices are used to provide valuable data with respect to the multiple elements that may affect sample quality. Using Method TO-15 and the NFG requirements as a basis, best practices for data validation of soil vapor data are presented below.

Sample Dilutions

Assessing the validity of sample data involves reviewing sample dilution factors to verify that they are reasonable based on the canister pressures upon receipt at the laboratory. Traditionally, analytical samples require dilutions for the following two reasons:

• Sample dilution can be the result of the addition of humidified zero air to the sample upon receipt at the laboratory to achieve a positive pressure in the canister, or a pressure that is slightly above ambient pressure. Typical positive pressure amounts are around 5 pounds per square inch (psi); however, no specific requirement exists. Laboratories often use the reasoning that older instruments perform better with canisters under a slight positive pressure, and some studies have shown that VOC analytes are more stable under a slight positive pressure (Coutant 1992). In addition, pressurization of canisters allows for more accurate sample loading, provides sufficient volume for reanalysis/dilutions, and reduces the chance of cross contamination of autosampler equipment. The amount of humidified zero air introduced to the sample canister is directly related to the amount of sample volume collected in the field. The more sample volume collected within the sample canister, the less humidified zero air that is added, resulting in less sample dilution. Therefore, the sampler should attempt to provide enough sample volume so that approximately 2 to 5 inHg remains in the canister at the end of sampling. As discussed previously, some residual vacuum should remain in the canister to allow for determination of leakage during transit from the field to the laboratory.
• A sample dilution can be the result of the laboratory analyzing a smaller sample volume. The decision to analyze a smaller sample size is usually the result of a highly contaminated sample or of compounds outside of laboratory calibration ranges.

A review of analytical data dilution factors can reveal several reasons for sample dilutions. However, when assessing the sample dilutions, the data user should discuss with the laboratory the reasoning behind the addition of makeup gas. In addition, the data user should speak with the laboratory about reporting limit requirements prior to sample collection. The conversation will allow the laboratory to provide information regarding the sample volume required to meet specific reporting limit requirements.

Instrumentation Quality Control

Depending on the method used, instrument quality control assessments may include some or all of the following: initial and continuing calibrations, instrument performance check results, and internal standard results.

Evaluating Calibration Results

Analytical calibration results are assessed to monitor the instrument’s initial and continued ability to successfully produce qualitative and quantitative data according to the analyte list. Method TO-15 defines dynamic calibration as “calibration of an analytical system using calibration gas standard concentrations in a form identical or very similar to the samples to be analyzed and by introducing such standards into the inlet of the sampling or analytical system from a manifold through which the gas standards are flowing.”

Instrument calibrations for air samples are analyzed in two parts. The first part is an initial calibration that consists of at least five concentrations of the target analytes, which span the monitoring range of interest. Second, the daily continuing calibrations are prepared and analyzed from the midpoint standard used in the initial calibration sequence. The continuing calibration verifies that the instrument has maintained the appropriate sensitivity and linearity established in the initial calibration. Assessments of calibration results are based on several of the following components (USEPA 2008).

Relative Response Factor (RRF) and Mean RRF: The RRF is a measure of the relative response of the instrument detector of an analyte compared to an internal or external standard. The RRFs are determined by the analysis of standards and are used to calculate the concentrations of analytes in samples. Since specific guidelines are not provided in Method TO-15, the NFG limits are used to evaluate the RRF and Mean RRF values. According to the NFG, the RRF and mean RRF values should be equal to or greater than 0.050, with the exception of the analytes noted in Table 15 of the NFG. The RRF values for these compounds should be equal to or greater than 0.01 (USEPA 2008).

Percent Relative Standard Deviation (%RSD): The %RSD is assessed using the initial RRF values. The %RSD is a measure of how precise the average is and how well the individual numbers agree with each other. Per the NFGs, most analytes must produce a %RSD less than 20%. However, Method TO-15 specifies that the %RSD be less than 30%. When validating air data, it is recommended that the %RSD limit of less than 30% be used since it is more difficult to produce precise results between air samples (as compared to water samples.). Additionally, the vapor phase standards used in method TO-15 are prepared with a higher error tolerance than the liquid phase standards used in analyses typically validated using the NFGs. For example, a vapor phase standard may have an error of approximately plus or minus 10% and a liquid standard may have an error of plus or minus 5%. Analytical results associated with continuing calibration %RSD values greater than 30% are qualified as J or UJ to indicate estimated concentrations or reporting limits.

Percent Difference (%D): The %D is assessed using the continuing calibration results. The %D is calculated between the initial calibration mean RRF and the continuing calibration RRF. Per the NFGs, most analytes must produce a %D that is less than 25%, with the exception of the analytes listed in Table 15, which must produce a %D that is less than 40%. However, Method TO-15 specifies that the %D be below 30%. When validating air data, it is recommended that the %D limit of less than 30% be used, with the exception of the Table 15 analytes, which should use a %D limit of less than 40%, since it is more difficult to produce precise results between air samples (as compared to water or soil samples).

When assessing the validity of air data, the procedures in Table 1, below, are recommended. The validator should verify that the frequency of calibration is in accordance with the method that is being used. (Method TO-15 requires that calibration verifications be analyzed every 24 hours.)

Table 1: Criteria for Reviewing Calibration Results

The J (for a detected value) and UJ (for an undetected value) flags indicate that the concentrations and contract required reporting limits are estimated. The estimated results may be inaccurate or imprecise, but are considered acceptable for use during a site assessment.

The R flag indicates that the results are rejected and should not be used during site assessment.

*Criteria for analysis was derived from the USEPA NFGs for Superfund Organic Methods Data Review and Method TO-15

**Flagging criteria were intended to model those established in the USEPA NFGs for Superfund Organic Methods Data Review

Evaluating Instrument Performance Check Results

For VOC analyses, the GC/MS instrument must meet tuning and standard mass spectral abundance criteria prior to initiating data analysis. The GC/MS system is set up according to the manufacturer’s specifications, and the mass calibration and resolution of the GC/MS system are then verified by the analysis of the instrument performance check standard, bromofluorobenzene (BFB) (USEPA 1999). In evaluating the instrument performance check data, the frequency of analyses should be evaluated. The instrument performance check standard should be analyzed before calibration standards and then as required by the analytical method. Method TO-15 requires the analysis and evaluation of the mass spectrum of BFB every 24 hours following the initial run.

Daily calibration sequences for the analysis of air samples begin with the injection of BFB. The calibration standard may be analyzed only if the BFB mass spectrum meets the ion abundance criteria. Table 2, below, includes important Method TO-15 evaluation criteria for BFB. When assessing the validity of data using the instrument tune results, the validator should reject results reported with an instrument tune outside of the criteria noted in Table 2, below, or those reported in the method employed.

Table 2: Criteria for Instrument Tune Results Mass Ion Abundance Criteria

*All ion abundances must be normalized to m/z 95, the nominal base peak, even though the ion abundance of m/z 174 may be up to 120% that of m/z 95.

Evaluating Internal Standard Results

Internal standard performance criteria are designed to ensure that GC/MS sensitivity and response are stable during each analysis (USEPA 2008). Internal standard spikes are injected with each field and quality control sample. Assessing the validity of internal standard results involves verifying that each sample was spiked with the applicable internal standard and assessing the area count results and retention times of the internal standards. Method TO-15 indicates that the area count of the internal standards should be within 40% of the mean area response over the initial calibration range. Additionally, Method TO-15 indicates that the retention times of the internal standards should not vary more than plus or minus 20 seconds of the mean retention time over the initial calibration range. Table 3, below, provides criteria for assessing internal standards.

Table 3: Criteria for Reviewing Internal Standard Results Criteria

The J (for a detected value) and UJ (for an undetected value) flags indicate that the concentrations and reporting limits are estimated.  The estimated results may be inaccurate or imprecise, but are considered acceptable for use during a site assessment.  

The R flag indicates that the results are rejected and should not be used during site assessment.

*Flagging criteria are intended to model those established in the USEPA NFGs for Superfund Organic Methods Data Review

Method Blank and Equipment Blank Samples

The purpose of blank analyses is to determine the existence and magnitude of contamination resulting from laboratory or field activities. The criteria for evaluation of blanks apply to any blank associated with the samples. If problems with any blank exist, all associated data must be carefully evaluated to determine whether or not there is an inherent variability in the data or if the problem is an isolated occurrence not affecting other data (USEPA 2008). When using 100% certified canisters, it is not necessary to collect trip blank or field blank samples.

Laboratory blanks can provide critical information on the validity of sample data and the source of contaminants and biases. Most analytical methods contain the following guidance: method blanks are analyzed with each analytical batch on a 1 per 20 sample basis or 1 per 24-hour period to evaluate possible contamination stemming from laboratory sources.

Equipment blank samples can be collected using helium passed through tubing or other equipment used in the field sampling process to check for contamination introduced by field sampling equipment.

Laboratory blank and equipment blank samples are analyzed identically to field samples. Table 4, below, can be used to determine if sample concentrations are authentic or possibly biased due to contamination from laboratory or field sampling equipment sources.

Table 4: Criteria for Reviewing Method Blank and Equipment Blank Samples

The U flag indicates that the analyte was estimated to be undetected at the contract required reporting limit.

The R flag indicates that the results are rejected and should not be used during site assessment.

The table above was derived from the USEPA Contract Laboratory Program NFGs for Superfund Organic Methods Data Review Table 18, with some deviations.  Common laboratory contaminants are not held to a different standard since they are not expected to be a source of laboratory contamination in a laboratory that analyzes air samples.  

CRQL: Contract Required Quantitation Limit

Accuracy

Laboratory accuracy is a measure of system bias and can be measured by evaluating laboratory control samples (LCSs) and deuterated monitoring compounds (DMC or surrogate) percent recoveries and oxygen results. Laboratory Control Samples The LCSs are analyzed to assess laboratory accuracy using a blank sample with known concentrations of prepared standards. The accuracy of the analytical data is measured by the LCS percent recovery.

Equation 1: Percent Recovery

where:

C_s = Measured concentration of the spiked sample aliquot

C_u = Measured concentration of the unspiked sample aliquot (use 0 for the LCS or surrogate)

C_n = Nominal (theoretical) concentration increase that results from spiking the sample, or the nominal concentration of the spiked aliquot (for LCS or surrogate)

While the analytical methods recommend limits for the laboratory control sample percent recoveries, laboratories often provide limits based on statistical analysis of samples analyzed by the laboratory over a set period of time in their results. When assessing the validity of analytical data, the laboratory’s statistically based limits should be used. In addition, the data qualification criteria in Table 5, below, should be considered when assessing the validity of LCS data.

Table 5: Criteria for Validating Laboratory Control Samples Criteria Flagging Criteria

The J (for a detected value) and UJ (for an undetected value) flags indicate that the concentrations and contract required reporting limits are estimated.  The estimated results may be inaccurate or imprecise, but are considered acceptable for use during a site assessment. 

The R flag indicates that the results are rejected and should not be used during site assessment.

*Flagging criteria are intended to model those established in the USEPA NFGs for Superfund Organic Methods Data Review.

Deuterated Monitoring Compounds

Laboratory performance on individual samples can be established by means of spiking the samples with DMCs. The sample itself may produce such factors as interferences (USEPA 2008). When DMCs are used in the analysis of samples collected in canisters, they cannot be considered to be true surrogates, as a true surrogate would follow a sample through the entire sample preparation. Since an air sample is not prepared (i.e., it is simply withdrawn from the canister, trapped and injected into the GC/MS system for analysis), and since the DMC compounds are added to the sample after the sample is withdrawn from the canister, DMCs for air samples do not necessarily have the same implications as DMCs for water or soil samples. Although none of the methods mentioned in this document require or mention the use of DMCs, USEPA Region 9 requires the use of DMCs for Method TO-15 (USEPA Region 9 2000). When DMCs are used, laboratories often provide limits based on statistical analysis of samples analyzed by the laboratory over a set period of time in their results. When assessing the validity of the analytical data, the laboratory’s statistically based limits should be used. In addition, the data qualification criteria in the Table 6, below, should be considered when assessing the validity of DMC recoveries.

Table 6: Criteria for Reviewing Deuterated Monitoring Compounds Recoveries Criteria Action

The J (for a detected value) and UJ (for an undetected value) flags indicate that the concentrations and contract required reporting limits are estimated.  The estimated results may be inaccurate or imprecise, but are considered acceptable for use during a site assessment. 

The R flag indicates that the results are rejected and should not be used during site assessment.

*Flagging criteria are intended to model those established in the USEPA NFGs for Superfund Organic Methods Data Review.

Assessing High Oxygen Results

Soil gas samples collected in canisters are often analyzed for VOCs, fixed gas analytes, and helium. Using one canister for all of these analyses may reveal certain problems with the fixed gas normalization calculations, particularly if helium has been used as a tracer. Historically, helium has been used by laboratories to pressurize canisters when oxygen is a target compound. However, when helium has been used as the tracer, the laboratory must use a different gas, typically nitrogen, to pressurize the canisters. The difficulties are illuminated when the canisters are pressurized with nitrogen upon arrival to the laboratory, since one of the analytes assessed in the fixed gas results is nitrogen. Following analyses, results for fixed gas analyses are normalized to 100%; therefore, the addition of nitrogen will increase that particular component and may cause other components to be high or low. When evaluating the validity and quality of fixed gas analyses, the following questions should be considered during the evaluation:

• What type of gas was used to pressurize the canisters?
• Can fixed gas samples be collected in a Tedlar bag instead of the canister used for VOCs and helium?
• Are oxygen results around 21%? These questions and associated concerns should be discussed with laboratory personnel before and during data evaluation procedures. Oxygen results that are just above 21% may be explained by coelution with argon, but results that are much higher may require qualification or rejection of data.

Precision

Precision is the measure of variability of individual sample measurements. Field precision is determined by comparison of field duplicate sample results. Laboratory precision is determined by examination of laboratory duplicate results. Evaluation of field and laboratory duplicates for precision is performed using the %RPD, defined as the difference between two duplicate samples divided by the mean and expressed as a percent.

Equation 2:  Relative Percent Difference

C₁ and C₂ are the concentrations of duplicate samples.

Field Duplicates

A field duplicate sample is collected simultaneously with the primary sample at one sampling location. The same sample collection techniques are used for both samples. When assessing data validity using field and laboratory duplicate results, Table 7, below, may be used.

Table 7: Criteria for Reviewing Field Duplicate Sample Results Criteria

The J (for a detected value) and UJ (for an undetected value) flags indicate that the concentrations and contract required reporting limits are estimated.  The estimated results may be inaccurate or imprecise, but are considered acceptable for use during a site assessment. 

*Flagging criteria are intended to model those established in the USEPA Region 1 Revised Data Validation Guidance (USEPA Region 1, 1996), while taking into account the replicate precision requirement of 25% noted in Method TO-15.

Laboratory Duplicates

A laboratory duplicate is determined from the analysis of two samples prepared from the same canister. Laboratories often provide limits for laboratory duplicates in their results that are based on statistical analysis of samples analyzed by the laboratory over a set period of time. When assessing the validity of the analytical data, the laboratory’s statistically based limits should be used. In addition, the data qualification criteria in the Table 8, below, should be considered when assessing the validity of laboratory duplicate RPDs.

Table 8: Criteria for Reviewing Laboratory Duplicate Sample Results

The J (for a detected value) and UJ (for an undetected value) flags indicate that the concentrations and contract required reporting limits are estimated.  The estimated results may be inaccurate or imprecise, but are considered acceptable for use during a site assessment. 

*Flagging criteria are intended to model those established in the USEPA Region 1 Revised Data Validation Guidance (USEPA Region 1, 1996).

Conclusions

The quality of soil vapor data is dependent on many factors, including media preparation, sampling technique, laboratory analysis, and validation of analytical results. In many cases, practitioners are being asked to provide data with very low reporting limits to allow for human health risk assessment of the vapor intrusion pathway. However, unlike soil and water analysis, the USEPA has not provided NFGs that are specific to the analysis of air. The aforementioned best practices establish a consistent approach for both improving, as well as validating, air data by providing specific guidelines for field methodologies and data validation approaches. Continued improvement in the evaluation and validation of air data will provide practitioners with defensible data that can be used to conduct vapor intrusion pathway assessments.

References

1. Advanced Global Atmospheric Gases Experiment. Available from:
   http://agage.eas.gatech.edu/index.htm.
2. Arizona Department of Environmental Quality (ADEQ). 2009. VOCs in Vapor by 8260B AZ Method, Revision 0.0, 04/14/2009. Available from:
   http://www.azdhs.gov/lab/license/tech/infoup.htm
3. Coutant, R. W. 1992. Theoretical Evaluation of Stability of Volatile Organic Chemicals and Polar Volatile Organic Chemicals in Canisters. Battelle.
4. Fortune, A. and Tuday, M. 2008. The Importance of Air Sampling Media Cleanliness for Vapor Intrusion Investigations. Presentation from National Environmental Monitoring Conference (NEMC), August 10-16, 2008, Washington, DC.
5. Interstate Technology and Regulatory Council. 2007. Technical and Regulatory Guidance Vapor Intrusion Pathway: A Practical Guide. Available from:
   http://www.itrcweb.org/guidancedocument.asp?TID=49
6. Massachusetts Department of Environmental Protection Bureau of Waste Site Cleanup (MassDEP). 2010. Quality Control Requirements and Petroleum Standards for the Analysis of Air-Phase Petroleum Hydrocarbons (APH) by Gas Chromatography/Mass Spectrometry (GC/MS) in Support of Response Actions under the Massachusetts Contingency Plan (MCP). Available from: http://www.mass.gov/dep/cleanup/laws/aphmcp.pdf
7. Minnesota Pollution Control Agency. 2008. Risk-Based Guidance for the Vapor Intrusion Pathway. Available from:
   http://www.pca.state.mn.us/index.php/component/option,com_docman/task,doc_view/gid,3162
8. Tuday 2008. Observations and Practical Experience in Soil Gas Analysis from a Laboratory Perspective. Presentation at the CA DTSC Soil Gas Advisory Forums, 2008. Presentation available at: http://www.dtsc.ca.gov/AssessingRisk/
9. United States Environmental Protection Agency. 1989. Compendium Method TO-14, Determination of Volatile Organic Compounds (VOCs) in Ambient Air Using Specially-Prepared Canisters with Subsequent Analysis by Gas Chromatography. No reference exists, superseded by Method TO-14A.
10. United States Environmental Protection Agency, Region 1. 1996. Revised Data Validation Guidance. Available from: http://www.epa.gov/region1/oeme/index.html
11. United States Environmental Protection Agency. 1999. Compendium Method TO-15, Determination of Volatile Organic Compounds (VOCs) in Air Collected in Specially-Prepared Canisters and Analyzed by Gas Chromatography/Mass Spectrometry (EPA/625/R-96/010b). Available from: http://www.epa.gov/ttnamti1/files/ambient/airtox/to-15r.pdf
12. United States Environmental Protection Agency. 1999. Compendium Method TO-14A, Determination of Volatile Organic Compounds (VOCs) in Ambient Air Using Specially-Prepared Canisters with Subsequent Analysis by Gas Chromatography (EPA/625/R-96/010b). Available from: http://www.epa.gov/ttnamti1/files/ambient/airtox/to-14ar.pdf
13. United States Environmental Protection Agency, Region 9. 2000. Volatile Organic Compounds (VOCs) in Air (Ambient Air/Soil Vapor/Stack Gas) Samples Collected in Specially-Prepared Canisters and Analyzed by Gas Chromatography/Mass Spectrometry (GC/MS). Available from: http://www.epa.gov/region9/qa/pdfs/dqi/vocs_gc.pdf
14. United States Environmental Protection Agency. 2002. OSWER Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils (Subsurface Vapor Intrusion Guidance) (EPA530-D-02-004), Appendix E. Available from:
    http://www.epa.gov/osw/hazard/correctiveaction/eis/vapor/complete.pdf
15. United States Environmental Protection Agency. 2008. USEPA Contract Laboratory Program National Functional Guidelines for Superfund Organic Methods Data Review (USEPA-540-R-08-01). Available from: http://www.epa.gov/superfund/programs/clp/download/somnfg.pdf
16. United States Environmental Protection Agency. 2009. USEPA Region 2 SOP HW-31 Revision 4 Validating Volatile Organic Analysis of Ambient Air in canister by Method TO-15 (SOP # HW-31). Available from: http://www.epa.gov/region2/qa/qa_documents/SOP%20HWSS-31.pdf
17. United States Environmental Protection Agency. 2010. USEPA Contract Laboratory Program National Functional Guidelines for Inorganic Superfund Data Review (USEPA 540-R-10-011). Available from: http://www.epa.gov/superfund/programs/clp/download/ism/ism1nfg.pdf

Interest in (ISM) has grown in recent years largely because the approach, when applied correctly, can significantly reduce sampling uncertainty. This in turn can increase the probability that sample data is more representative of average site conditions at hazardous waste sites, thereby strengthening decision making at the site.

DoD Directive 4715.11 requires an assessment of munitions on operational firing ranges and the Military Munitions Response Program (MMRP) requires similar assessments of closed ranges. These requirements have historically been met by dividing the sites into exposure units and collecting discrete or small-scale composite samples for explosives analysis by EPA Method 8330A. Results were assumed to be normally distributed and representative of the entire exposure unit. The U.S. Army Corp of Engineers Cold Regions Research and Engineering Laboratory (CRREL) demonstrated that these assumptions were false. Traditional field sampling and laboratory sub-sampling methodologies are not able to accurately represent conditions at the site. As a result, improved sampling methodologies became a priority.

Aspects of ISM have been utilized for several years. The work on surface soil sampling at DoD firing ranges and relevant methodologies were published in 2007 by CRREL in a document titled “Protocols for Collection of Surface Soil Samples at Military Training and Testing Ranges for the Characterization of Energetic Munitions Constituents.”  State regulatory agencies have started to adopt and issue guidance for using MIS protocols at hazardous waste sites, and these guidelines are encompassing broader constituents than explosive residues (Alaska DEC, Hawaii DoH HEER, Ohio EPA VAP). The Interstate Technology Regulatory Council (ITRC) began working on ISM in 2009 and is scheduled to issue guidance in early 2011. Several states are represented in this workgroup including Florida, California, Massachusetts, Texas, Oklahoma, Arizona, and New Mexico. These activities are expected to increase interest and use of ISM at hazardous waste sites around the country.

Technical Review

On the surface, ISM might be confused with more traditional compositing techniques; but this assessment misses the point of incremental sampling. It is designed to statistically reduce or limit the variability associated with discrete sampling. This variability is attributed to compositional and distributional heterogeneity. Composite sampling with limited increments does not adequately address these issues. It tends to add uncertainty unless the entire sample is already homogeneous (an unlikely occurrence in the field).  ISM differs from typical composite sampling in two ways: (1) the number of grabs is much greater, and (2) the combined grabs represent the entire area of interest (defined as a decision unit). This process is controlled through a detailed sampling plan.

Heterogeneity introduces error to the sampling process; ISM addresses the two main sources of sampling error attributed to heterogeneity (refer to figure 1 for a comparison of discrete and incremental sampling).

• Compositional heterogeneity describes the distribution of contaminant concentration across the range of particle sizes making up the population. It introduces “fundamental error” (FE) when insufficient mass is collected and analyzed. ISM addresses this source of error by controlling the sample size that is collected and analyzed.
• Distributional heterogeneity is a function of spatial variability and occurs when particles are not randomly distributed across the population. It introduces “grouping and segregation error” (GSE) when the sample consists of too few increments to capture or represent the spatial variability. ISM addresses this source of error through the collection of multiple, randomly located sample increments.

Figure 1. ISM is designed to better control FE and GSE

There are two components to ISM: field sampling and laboratory analysis. In the field, an approximately 1 – 5 kg sample is collected and sent to the laboratory for processing in its entirety. Thirty to 100 increments (or more depending on the expected distributional heterogeneity for the decision unit) of uniform size are collected across a grid formation that represents the entire decision unit. Determining the appropriate size of the decision unit is a critical aspect of ISM and one that is usually detailed in a sampling plan that is reviewed and approved prior to field mobilization. Some sampling plans may require that the sample be field dried and size reduced; but more often, the entire 1 – 5 kg sample is delivered to the laboratory for additional processing.

In the lab, the sample is processed in accordance with program requirements, site specific sampling plans, or by the laboratory’s SOP. In general, these procedures include air drying, sieving, particle reduction (grinding or milling), and a multi-increment sub-sampling performed in accordance with established guidelines. The entire sample is spread into a grid formation and the sub-sample is generated using similar techniques employed in the field, only on a much smaller scale. The sub-sample is typically in the 10-30g size. Alternatively, some sampling plans will allow the use of a sample splitter (e.g., rotary riffle splitter or equivalent). Essentially the same objective is achieved regardless of the technique used.

This entire sub-sample is used for analysis. Batch QC includes replicate analysis to verify homogeneity; multi-incremental sample replicates are usually normally distributed with very few outliers. Thus, the goal of limiting discrete sample variability is achieved.

ISM may not be appropriate to apply universally at a site. It was designed as a surface sample collection technique, with the goal of reducing sources of sampling error for the entire decision unit. More than one sampling approach may be applicable for complete site characterization. For example, ISM may be useful in characterizing surface soils, excavation floors and walls, or contaminated stockpiles, but not for meeting other site characterization goals. Sampling guidelines issued by state and federal agencies will typically include details about the use of ISM in site characterization.

Method and/or Analyte  Class Considerations

EPA Method 8330B has incorporated ISM. This was a significant change when compared to the previous method, 8330A. Method 8330B requires air drying and sieving of samples to less than 2 mm. The protocol then requires milling when samples are collected at firing range sites, or mortar and pestle grinding for ammunition plans and depots. The Department of Defense has issued specific guidelines for implementing EPA SW-846 8330B to address sampling and analytical methodologies, concepts, and QC requirements of the method.

There are a few key differences between different versions of EPA 8330x:

• 8330 and 8330A produce detection limits ~10x higher than 8330B due to differences in the extraction procedures;
• All versions of the method require air-drying, sieving, and grinding, but only 8330B requires ISM protocols;
• Grinding procedures differ by sample source:
  • mortar and pestle for ammunition plants and depots,
  • ring puck mill or equivalent mechanical grinder for firing ranges;
• 8330B always requires ISM, regardless of the sample source.

EPA Method 8330B is currently the only method with specific guidance on the use of ISM to reduce sampling error. The concepts may apply to other groups of analyses.  Sampling and analysis plans should include procedural guidelines to ensure that field and laboratory applications meet data quality objectives at the site. The use of milling or grinding will not be appropriate for all classes of target analyses. For example, milling may be appropriate for explosives and metals, but inappropriate for volatile organics.  State specific guidelines (in Alaska, Hawaii, and Ohio) are useful in assessing the applicability of ISM and considerations that must be taken into account during the development of the sampling plan. These guidelines include information on analyte-specific considerations, minimum sub-sample size for analysis, and techniques for obtaining a representative sub-sample.

Alaska and Hawaii include volatile organics in state specific ISM guidance documents.  The procedure for collecting the ISM sample for volatiles includes preservation in methanol. This precludes low level sample analysis, thereby resulting in detection limits that may be significantly higher than data quality objectives for other states. Therefore, ISM may not be appropriate for collection of volatile organics outside of a narrow application.

The US Army Corp of Engineers is actively conducting research and demonstration projects to evaluate the use of ISM on a number of contaminated sites. Contaminants of concern include metals, polycyclic aromatic hydrocarbons, perchlorate, and white phosphorous. Each of these classes of compounds presents unique sampling challenges.  Sampling plans should be written to include guidance to assess sampling precision in the field and in the laboratory.

Benefits and Limitations

According to the National Defense Center for Energy and Environment (NDCEE), benefits of ISM include:

• The approach adds flexibility to the planning process as regulators and stakeholders evaluate the configuration and the number of decision units needed to characterize the site;
• Depending on the size of a decision unit, ISM sampling can reduce the number of samples being analyzed at the site thereby reducing analytical costs;
• The process offers improved precision (e.g., lower relative standard deviation between field replicates and between laboratory replicates) indicating that ISM sampling provides a more accurate representation of average site conditions;
• More representative data supports effective decision making;
• Indirect cost benefits are derived from the higher level of confidence in the data (i.e., consistency of data across sampling events, fewer anomalies, and more informed decision making).

There are a few limitations that need to be considered:

• Limited acceptance and regulatory guidance still exists, although this is changing as more agencies integrate ISM into sampling guidance documents;
• Sampling plans have to define the decision unit to be composited into a multi-incremental sample;
• Fewer labs have the capability to process ISM samples;
• Cost per analysis is higher to account for additional processing steps, although this cost is usually off-set by fewer samples per investigation;
• The technique is not appropriate for all analyte classes or sample types (e.g. shallow surface soil sampling has been evaluated, but cost benefits should be re-examined for deeper sampling).

Regulatory Acceptance and Guidance Documents

• State of Alaska Department of Environmental Conservation, Division of Spill Prevention and Response, Contaminated Sites Program, Draft Guidance on Multi-Incremental Soil Sampling, March 2009
• State of Hawaii Department of Health, Office of Hazard Evaluation and Emergency Response, Technical Guidance Manual for the Implementation of the Hawaii State Contingency Plan, Section 4: Soil Sample Collection Approaches, November 2008
• US Army Corps of Engineers Interim Guidance 09-02, 20 July 2009, Implementation of Incremental Sampling (IS) of Soil for the Military Munitions Response Program
• Ohio EPA Division of Emergency and Remedial Response, Standard Operating Procedure 2.6.1: Multi-Incremental Sampling for Soils and Sediments, January 2007
• Interstate Technology Regulatory Council, Project Introduction: Incremental Sampling Methodology, July 2009
• National Defense Center for Energy and Environment, Office of the Assistant Secretary of the Army for Installations, Energy and Environment, Concurrent Technologies Corporation, Multi-Incremental Fact Sheet

For more information visit Incremental Sampling.

By Jeff Grindstaff and Colleen Schroeder

Changes to heavy metals test procedures for the analysis of pharmaceuticals and dietary supplements are under review with new standards set to be in place by mid-2013.⁴ The intention of the review is to update current analytical testing historically performed using United States Pharmacopeia (USP) <231>. The revisions (USP<232>, USP<233>, and USP<2232>) are designed to set safer limits for public exposure and to reduce the environmental impact of dated methods. Many in the pharmaceutical industry have concerns about the new instrumentation, more stringent requirements, and the associated costs. Nonetheless, the revisions should have a beneficial impact on the industry by significantly improving specificity and analyte recoveries, as well as by yielding overall time savings resulting in safer, higher quality products.

Shift from Outdated Technology to Modern Methodology

First introduced over 100 years ago, USP<231> is a colorimetric procedure based on the precipitation of insoluble metal sulfides. The test is qualitative rather than quantitative. It is not an element specific method, nor is it equally sensitive to each metal. The limits specified by the test are based on the ability to observe the precipitate, rather than on the analysis of toxicological data. The procedure does not necessarily detect all potential forms and/or valences of elements of concern when they are present as the oxo ions or in the organometallic form. Chromium and nickel are potential contaminants from modern stainless steel processing equipment and are not detected by USP<231>. Other studies indicate inconsistent recoveries of monitor and standard solutions using USP<231> method II.^{2, 3}

Industry criticism of this dated method began around 15 years ago and sparked the revision process by the USP. After seeking public comment and advice from experts on metals toxicology, the USP is now recommending that USP<231> be revised to USP<232>, which will require the use of updated instrumental technology to improve selectivity and sensitivity. The change includes modification to the preparation and analysis methodology as well as the impurity limits of each analyte.

Revisions to the elemental impurities test will constitute a serious change for the pharmaceutical industry. The change will shift the testing from a relatively inexpensive procedure that requires minimal set-up and operator training to tests that require expensive instrumentation and highly skilled metals analysts. However, by employing modern instrumental methods, the USP’s intent is to ensure safer products for the consumer as well as offer flexibility and efficiency during testing.

All drug products produced and sold in the U.S. will have to comply with the limits set by USP<232>, and drug substances and excipients will have to be tested and reported for elemental impurities. Likewise, all nutraceutical products will have to comply with limits set by USP<2232>, which includes guidelines for speciating organic and inorganic forms of various elements. USP<232>, USP<233> and USP<2232> are currently in a preliminary recommendation stage and the limits described have not been finalized.

Improved Methodology for Identifying Discrete Elements

One of the main criticisms of USP<231> has been the inability of the testing to recover and identify individual elements. Previously, the elemental impurity list included arsenic, antimony, bismuth, cadmium, copper, lead, mercury, molybdenum, silver and tin due to reactivity of these metals with the sulfide ion utilized in the procedure. The metals were reported inclusively as “heavy metals” due to the procedural inability to show them discretely. In addition, arsenic, bismuth, and molybdenum were not necessarily detected by USP<231> due to common occurrences of these elements in forms inert to the mechanism in the procedure. Since numerous instrumental procedures have been developed over the life of USP<231> that incorporate significant improvements in selectivity and sensitivity, the USP’s proposal will require individual quantification of arsenic, cadmium, lead and mercury (target elements considered most toxic to humans and the environment, see Table 1). If the presence of additional metals is suspected (for instance, if used in the manufacturing process as catalysts or if detected during previous testing), then those additional metals would be added to the target list. Each element screened will have individually distinct impurity limits, based on unique toxicity data.^5,6

The USP is considering many factors to decide which elements will be tested and at what levels. The likelihood of contamination during manufacturing, possible additional environmental exposure, as well as reactions with other metals (co-exposure) during drug administration are factors influencing the review. Though rapid, accurate, simultaneous multi-element analysis of many metals is now possible at very low concentrations, the USP has preliminarily decided to base impurity limits on toxicologically relevant data in an effort to avoid burdening the industry with unnecessarily low limit requirements. The new limits will be based primarily on previously established guidelines for human and animal toxicological exposure and are dependent on route of delivery (see Table 2). Screening will be required for all toxic metals that have been shown to be present, regardless of whether or not they are included in the impurities list. However, the USP will not mandate methodology. Each manufacturer will be able to choose the procedure(s) that best fits their processes.

USP<233> Methodology

In moving from a chemical to an instrument based methodology, the USP has taken great care to allow for a flexible approach and is working closely with both the FDA and industry to ensure widespread agreement on interpretation of the revisions. Following are brief descriptions of the methodologies being proposed.

Sample Preparation

Sample preparations range from relatively simple acidification and direct injection to more complex total oxidations/dissolutions performed under elevated temperature and pressure in appropriate acid(s) to assure dissolution of target elements. Sample preparations are intended to yield an aqueous digestate suitable for instrumental analysis via one or more instrumental techniques.^4,7 (See Figure 1 for a decision tree on sample preparation and analysis.)

Figure 1. Sample Preparation Decision Tree

-

Instrumentation

The techniques typically utilized for the analysis of the sample digestates are Cold Vapor Atomic Absorption (CVAA), Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP/OES), and/or Inductively Coupled Plasma-Mass Spectrometry (ICP/MS). Technical considerations beyond the scope of this discussion dictate the choice of procedures. As with any analytical technique, interferences (chemical and/or physical) exist with each technique. Intelligent decisions relative to the elements of interest and the sample matrix will indicate the appropriate analytical approach.

Although the majority of applications can be satisfied by the use of ICP/MS and/or ICP/OES, expert trace metals chemists recognize that alternative procedures are required at times to satisfy unusual analytical challenges. Careful examination of each application must be done from a quality assurance perspective. There are situations when multi-element techniques that utilize the plasma as an ion source or light emission source are capable of producing values that appear to be valid from a quality control standpoint, but are nonetheless invalid from a quality assurance standpoint. On these occasions, the following instrumental techniques still play a role in a fully functional trace metals laboratory: Purge & Trap Cold Vapor Atomic Fluorescence Spectroscopy (P&T-CVAFS), Graphite Furnace Atomic Absorption (GFAA), Flame Atomic Absorption (FLAA), and Gaseous Hydride Atomic Absorption (GHAA).

The revised quantitative methods, though of great benefit in terms of accuracy and recovery, are significantly more expensive than the qualitative USP<231>. Perhaps the main criticism of the revised testing protocols relates to the associated cost of new instrumentation and/or outsourcing for testing. Because atomic spectroscopy and ICP spectrometry are not yet widely used in the pharmaceutical industry, smaller manufacturers and excipient companies may not yet have the instrumentation in place and will need to either purchase the new equipment or send their testing to contract laboratories.

The various instrumental techniques each include advantages and disadvantages with respect to cost, sensitivity, selectivity, and ease of use. Some of the techniques are best suited for certain elements, but not for others. The same is true for certain sample matrices. For example, the analysis for lead and arsenic by ICP/OES or FLAA frequently represents a poor choice because of the associated high detection limits (DL). With these elements sample preparation would have to be more complicated in order to offset relatively high DL for the instrumentation. Alternatively, GFAA or ICP/MS would be preferable choices.

The instruments listed in Table 3 are capable of performing analysis of some or all of the elements listed in USP<232>. This table compares the instruments and equipment most commonly required to meet the USP requirements. Approximate values representing initial purchase and ongoing operating costs as well asl abbreviated summaries of strengths and weakness are also listed.

-

Validation of Quantitative Procedures

Verification of the compendial procedures indicated in USP<233> will be required prior to use. This can be completed by meeting the “Procedure Validation Requirements” outlined in USP<233>.⁴ Two types of validations (limit and quantitative) will be permitted. The limit test validation will include limit of detection, precision, and specificity. The quantitative test validation will include performing accuracy, precision, specificity, limit of quantitation, range and linearity. Both types of validations will need to be verified experimentally. In addition, sample preparation not specified in the monograph will also require verification. The compendial procedures encompass both ICP/OES and ICP/MS technologies, and the general instrumental and suitability requirements for each procedure are specified for users. Laboratories will be able to choose the appropriate technology that best fits their needs.

Summary

Although USP<233> represents a major shift for the pharmaceutical industry, U.S. Pharmacopeia has clearly stated they do not intend to create a system of unnecessary and complicated requirements.⁵ The goal is simply to create standards for safer pharmaceutical products and dietary supplements, through the use of modern technology. While increased cost is a factor, and manufacturers will need to make certain adjustments, this shift represents an appropriate modernization that manifests itself by assuring higher quality products.

References:

1. Raghu ram, P. “IPC-USP 75th Annual Scientific Meeting 2008.” USPOrg. 2008. Hetero. http://www.usp.org/pdf/EN/meetings/asMeetingIndia/2008Session4track2.pdf. Last accessed Januray 20 2011.
2. Lewen, Mathew, Schenkenberger, Raglione. “A Rapid ICP-MS Screen for Heavy Metals in Pharmaceutical Compounds.” J. Phar. & Biomed, Anal. 35 (2004) 739-752.
3. Lira, Sergio, Peter Brush, Laurence Senak, Chi-san Wu, Edward Malawer. “The Use of Inductively Coupled Plasma-Optical Emission Spectroscopy in the Determination of Heavy Metals in Crospovidone and Povidone as a Replacement for the Concomitant Visual Comparison Test.” Pharmacopeial Forum Vol. 34(6)[Nov.-Dec. 2008].
4. US Pharmacopeia Hot Topics Elemental Impurities Revised October 6, 2010. http://www.usp.org/hottopics/metals.html. Last accessed January 25, 2011.
5. Elemental Impurities. Pharmacopeial Forum Vol. 36(1)[Jan.- Feb. 2010]
6. Lenntech, Home Page, http://www.lenntech.com/periodic/periodic-chart.htm, January 19, 2011
7. Standard methods for the examination of water and wastewater. 20th ed. American. Public Health Association, Washington, D.C. 4. Horwitz, W. (ed.) 2000.
8. Stellmack, Mary and Dr. Kent Rhodes. “Metal Contamination in Biopharmaceutical Drugs: Solving a puzzle without all the pieces.” The McCrone Group. October 1, 2010.  McCrone Associates Inc. http://www.mccrone.com/media/2010/10/14. Last accessed January 19, 2011.
9. Taylor, Howard E. Inductively Coupled Plasma-Mass Spectrometry, Practices and Techniques. San Diego: Academic Press, 2001.
10. Pedersen, Ole. Pharmaceutical Chemical Analysis: Methods for Identification and Limit Tests. Boca Raton: CRC, 2006.
11. Wilbur, Steve. “A Comparison of the Relative Cost and Productivity of Traditional Metals Analysis Techniques Versus ICP-MS in High Throughput Commercial Laboratories.” Agilent. 2005. Agilent Technologies. http://www.chem.agilent.com/Library/applications/5989-1585EN.pdf. Last accessed January 20, 2011.
12. Agency for Toxic Substances and Disease Registry (ATSDR). ATSDR.CDC.Gov.  http://www.atsdr.cdc.gov/ToxProfiles/index.asp. Last accessed January 20, 2011.
13. Electronic Code of Federal Regulations (e-CRF). http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&tpl=%2Findex.tpl. Last accessed January 20, 2011.

- – -

This article appeared in Drug Development & Delivery magazine. Click to view…

Learn more about Testing Heavy Metals USP<231>…

On June 14, 2010, ASTM International (formerly the American Society for Testing and Materials) issued E 2600-10, Standard Guide for Vapor Encroachment Screening on Property Involved in Real Estate Transactions. This document revises and supersedes ASTM E 2600-08, Standard Practice for Assessment of Vapor Intrusion into Structures on Property Involved in Real Estate Transactions, issued on March 3, 2008.¹

Vapor intrusion – and/or vapor encroachment – from subsurface sources onto parcels of real estate and the resulting concerns with health hazards and potential liabilities have become an increasingly significant issue within the environmental consulting industry.² ASTM published the 2008 Standard Practice to address these concerns, but, according to some observers, the 2008 Standard resulted in “confusion in the marketplace.”  For instance, real estate and environmental professionals wanted to know whether E 2600-08 was a screening standard or an assessment standard, and how the standard was related to ASTM’s Phase I Environmental Site Assessment (ESA) Standard (E 1527-05). ASTM therefore issued the 2010 Standard Guide.³

The Interstate Technology and Regulatory Council (ITRC) has defined vapor intrusion as “the migration of volatile chemicals from the subsurface into overlying buildings. Volatile chemicals may include volatile organic compounds, select semivolatile organic compounds, and some inorganic analytes, such as elemental mercury and hydrogen sulfide.”⁴

In the new standard guide, ASTM defines a vapor encroachment condition (VEC) as the presence or likely presence of vapors from chemicals of concern (COC) in the subsurface of a property caused by the release of vapors on or near the property.⁵

Anthony Buonicore, who chaired the ASTM work group on vapor intrusion, stated that the 2008 standard was criticized for going beyond the scope of its original intent, which had been as a screening tool. Mr. Buonicore stated that the new standard will be more streamlined, containing two tiers for determining whether a property has the potential for vapor intrusion rather than the four tiers included in the earlier version.⁶ Finally, Mr. Buonicore said that the revisions of the 2008 Standard were to improve “practicality, clarity and consistency.”⁷

The Environmental, Safety & Toxic Torts Group of Seyfarth Shaw, LLP, stated that the 2010 Standard appears to act as a screen for determining the possibility of vapor intrusion, while the 2008 Standard included an actual assessment of the presence of vapor intrusion and recommended actions to address this condition. Seyfarth Shaw stated further that the 2010 Standard is a guide that helps establish whether a VEC exists, likely exists, can be ruled out, or cannot be ruled out.⁸

Environmental Attorney Laurence Kirsch of Goodwin Proctor, LLP, concurred that the 2008 Standard was intended as a screening tool, and also stated that the 2008 Standard was considered too prescriptive and created confusion among the intended users, including insurers, lenders and buyers involved in property transactions. Environmental Attorney Larry Schnapf of Schnapf Law, LLC, said that vapor intrusion has become a source of lawsuits, and that it appears as though “it is becoming the new asbestos.” Mr. Kirsch and Mr. Schnapf served as co-chairs of the legal committee working on the Vapor Encroachment Screen Standard.⁹

The new ASTM Standard Guide addresses the need for clarification in the vapor intrusion area. The Environmental Protection Agency’s (EPA) most recent substantive effort towards providing direction was a draft of an Office of Solid Waste and Emergency Response vapor intrusion guidance document released in 2002.¹⁰ This document provides technical and policy recommendations for evaluating subsurface vapor intrusion. It is notable that the document in still in draft form and to date has not been finalized.

There are indications that the EPA itself is dissatisfied with this 2002 draft document both because of its limitations of purpose and scope and outdated technical information. This is best demonstrated by the title of an Evaluation Report released on December 14, 2009 by the EPA’s own Office of Inspector General, Lack of Final Guidance on Vapor Intrusion Impedes Efforts to Address Indoor Air Risks.¹¹ The EPA stated that it expects to issue a final version of its vapor intrusion guidance by November 2012, and recommends using “the 2002 draft and other available sound scientific information to address vapor intrusion in the interim.”¹²

In the meantime, other federal entities and a growing number of states have published their own vapor intrusion guidance documents. For example, in 2009 the U.S. Department of Housing and Urban Development’s (HUD) Guide to Multifamily Accelerated Processing (MAP Guide) added a vapor intrusion screen amendment to the Phase I ESA already required for multifamily housing loans.¹³ In January, 2009, the Tri-Service (Army, Navy, Air Force) Environmental Risk Assessment Work Group issued the Department of Defense Vapor Intrusion Handbook.¹⁴ A Vapor Intrusion Indoor Air Survey prepared for the Massachusetts Department of Environmental Protection in April, 2010, revealed that at the time of the survey 29 of the 50 U.S. states had specific vapor intrusion guidance policies.¹⁵

Finally, the ITRC Vapor Intrusion Team, composed of representatives from 19 state environmental agencies, 12 environmental companies, and 4 federal agencies, including the EPA, addressed this issue by developing two Vapor Intrusion Pathway documents, A Practical Guide (VI-1, 2007) and Investigative Approaches for Typical Scenarios (VI-1A, 2007).¹⁶

The large number and variety of guidance documents indicates that one of the advantages of the ASTM E2600-10 Standard Guide is that it provides a standardized methodology to evaluate the potential for vapor encroachment on properties.¹⁷

The new Standard features a two-tiered approach to vapor encroachment screening. Information collected during Tier 1 vapor encroachment screening is similar to that collected during a Phase I ESA investigation and includes such information as:

• Federal, state, local, and tribal government records;
• Chemical use records and prior use records of the property and the area of concern;
• Soil, geological, and contaminant characteristics;
• Contaminant plume migration and possible pathways;
• Groundwater depth and flow; and
• Property information data.

If a VEC cannot be ruled out by Tier 1 screening, the user may proceed to the Tier 2 process. Tier 2 requires a more refined screening that uses numeric data gained through evaluation of existing files and documents or collected by sampling the soil, soil gas, and/or groundwater of the property.¹⁸

When Tier 2 screening involves sampling, labs such as Columbia Analytical Services can provide analytical expertise and project management capabilities to support a variety of soil vapor intrusion and indoor air investigations.¹⁹

Anthony Buonicore, the chair of the ASTM Vapor Intrusion work group, anticipates that the screening under ASTM E 2600-10 will eventually become a routine part of an All Appropriate Inquiry-compliant Phase I ESA.²⁰

References:

1. ASTM International. Standards. Vapor Encroachment Screening. http://www.astm.org/Standards/E2600.htm
2. Civil & Environmental Consultants, Inc. Jennifer A. Ewing, P.G. November 1, 2010.http://cecinc.wordpress.com/
3. Environmental Protection. Vapor Intrusion and ASTM’s Revised Vapor Encroachment Standard. Dianne P. Crocker. December 6, 2010.
   http://eponline.com/articles/2010/12/06/vapor-intrusion-and-astms-revised-vapor-encroachment-standard.aspx
4. Interstate Technology & Regulatory Council. Vapor Intrusion Webpage. Accessed on December 15, 2010. http://www.itrcweb.org/teampublic_Vapor.asp

1. ASTM International. Standards. Vapor Encroachment Screening. http://www.astm.org/Standards/E2600.htm
2. Bureau of National Affairs. EPA Vapor Intrusion Guidance, ASTM Standard Forthcoming. May 20, 2010. http://subscript.bna.com/pic2/eddg.nsf/id/BNAP-86SK2T?OpenDocument\
3. Pollution Engineering. A Smaller Intrusion. Anthony Buonicore, May 1, 2009. http://www.pollutionengineering.com/Articles/Article_Rotation/BNP_GUID_9-5-2006_A_10000000000000586701
4. Seyfarth Shaw, LLP. ASTM Changes “Vapor Intrusion Assessment” into “Vapor    Encroachment Screening. Accessed on December 5, 2010. http://www.seyfarth.com/index.cfm/fuseaction/home.home/home.cfm
5. Bureau of National Affairs. EPA Vapor Intrusion Guidance, ASTM Standard Forthcoming. May 20, 2010. http://subscript.bna.com/pic2/eddg.nsf/id/BNAP-86SK2T?OpenDocument
6. EPA. Vapor Intrusion Guidance. Updated on August 27, 2008. OSWER Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils (Subsurface Vapor Intrusion Guidance)
7. EPA Office of Inspector General. Vapor Guidance Evaluation Report. December 14, 2009. http://www.epa.gov/oig/reports/2010/20091214-10-P-0042.pdf
8. EPA OSWER Vapor Intrusion Page. Updated August 30, 2010 http://www.epa.gov/oswer/vaporintrusion/
9. HUD MAP Guide. Chapter 9. September 18, 2009 http://www.hud.gov/offices/hsg/mfh/map/mapguide/chap09.pdf
10. EPA Contaminated Site Clean-up Information. Vapor Intrusion. January, 2009. http://www.clu-in.org/download/char/dodvihdbk200901.pdf
11. Massachusetts Department of Environmental Protection. Vapor Intrusion Indoor Air Survey. April, 2010 http://www.mass.gov/dep/cleanup/laws/visurv.pdf
12. Interstate Technology & Regulatory Council. Vapor Intrusion Webpage. Accessed on December 15, 2010. http://www.itrcweb.org/teampublic_Vapor.asp
13. Environmental Protection. Vapor Intrusion and ASTM’s Revised Vapor Encroachment Standard. Dianne P. Crocker. December 6, 2010.
    http://eponline.com/articles/2010/12/06/vapor-intrusion-and-astms-revised-vapor-encroachment-standard.aspx
14. Civil & Environmental Consultants, Inc. Jennifer A. Ewing, P.G. November 1, 2010. http://cecinc.wordpress.com/
15. Columbia Analytical Services, Inc. Subsurface Vapor Intrusion to Indoor Air http://www.caslab.com/Forms-Downloads/Flyers/SUB_VAPOR_INTRUSION_FLYER.pdf
16. Commonground. EDR. Anthony Buonicore. June 17, 2010 http://commonground.edrnet.com/posts/b6a2475b19

In a memo dated January 11, 2011 the EPA recommended that all PWS request their laboratories use a modified version of EPA Method 218.6, “Determination of Dissolved Hexavalent Chromium in Drinking Water, Groundwater and Industrial Wastewater Effluents by Ion Chromatography” (Rev. 3.3, 1994; www.nemi.gov) when testing drinking water samples. These modifications allow for improved low concentration measurement and are outlined in Dionex Corp. Application Update 144 “Determination of Hexavalent Chromium in Drinking Water by Ion Chromatography” found at www.dionex.com/en-us/webdocs/4242-AU144_V18.pdf. With appropriate modifications, laboratories are capable of attaining a detection limit as low as California’s proposed public health goal of 0.02 µg/L (ppb) and can support the EPA’s recommended reporting limit of 0.06 µg/L (ppb).

The holding time for a sample to be tested for chromium-6, under method 218.6, is 24 hours. However, as part of EPA’s guidance on hexavalent chromium, they issued a temporary extension for chromium-6 drinking water samples to 5 days, provided samples are properly collected and treated with an ammonium sulfate/ammonium hydroxide buffer to maintain an alkaline pH in the 9.0 to 9.5 range. The EPA stated that the holding time of 24 hours prescribed in Method 218.6 was based upon the most conservative holding times for wastewater and sludge extracts, also covered by the method, and not the stability of chromium-6 in drinking water matrices. However, the State of California has questioned the ability of the buffer to stabilize chromium-6 for 5 days and is currently performing studies to answer that question.

It is important to emphasize that, in spite of the EPA’s guidance document, the lowest total chromium maximum contaminant level (MCL) required anywhere in the US, except for California, is 100 ppb. In California the regulated level is 50 ppb for total chromium. Under the existing regulations, total chromium testing does not distinguish between how much of the total chromium is chromium-6 (the chromium form considered toxic) and how much is chromium-3 (an essential nutrient in our diets).

If a water agency wants to be prepared for the possible lowering of the MCL, they will need to determine which level they want to measure and identify a laboratory capable of meeting those detection limits. Possible changes to the MCL include the adoption of:

• California’s MCL of 50 ppb for total chromium,
• EPA’s recommended level of 0.06 ppb for chromium-6, or
• California’s newly proposed public health goal of 0.02 ppb for chromium-6.

In an effort to address the availability of laboratories that can currently meet the required detection limits, the EPA has stated they will accept data from any lab that is certified by a state, by the National Environmental Laboratory Accreditation Program (NELAP) or by a federal agency to perform an approved ion chromatography method and meet the detection limits of either 0.02 ppb or 0.06 ppb for chromium-6.¹

The EPA is continuing to assess the new data and plans to issue a final assessment on chromium-6, in accordance with the Safe Drinking Water Act, sometime this year.

Columbia Analytical can meet the most stringent detection limit requirement. Visit this site for more information on testing for hexavalent chromium.

¹ “Laboratories that have the necessary equipment and are certified by an accrediting authority to conduct an approved ion chromatography method (e.g., EPA Method 300.0, SM 4110B, ASTM D4327) should be given preferential consideration to provide this analytical support”; Hexavalent Chromium in Drinking Water EPA Guidance Information, How can I find a laboratory to measure chromium-6? http://water.epa.gov/drink/info/chromium/guidance.cfm, January 2011