Environmental Analysis Methods and Instrumentation

Total and the ASTM D7365 Challenge Matrix

2011-09-16T07:50:00.003-07:00

So far I have not been able to find a single total cyanide method that perfectly determines only total cyanide without either generating or destroying cyanide in the process. I have written about this problem in several other ezine articles. The ASTM developed a matrix that is known to generate cyanide during total cyanide digestions and suggests that it be used to evaluate all cyanide methods. I have sent this matrix out to several laboratories, who will remain un-named, and the following results are typical for this matrix:

EPA 335.4 recovers about 60 - 80 ppb on average. Laboratories reported spike recoveries in the 90 - 110 % range. Remember, this matrix does not contain cyanide.

EPA 335.2 recovers a little more, usually somewhere between 80 and 100 parts per billion.

ASTM D7284 recovers less, usually between 50 - 70 ppb.

Kelada 01 recovers a lot more, usually between 500 - 1000 ppb.

ASTM D7511 recovers less, usually between 20 - 50 ppb.

The ASTM D7511 reagents can be modified. This modification of the reagent recipe improves recovery of total cyanide from iron complexes and decreases the generation of cyanide from the challenge matrix. Using the modified reagents recovers 15 - 25 ppb CN from the ASTM challenge matrix.

As cyanide effluent limits get lower and lower it is important to use methods that don't falsely report cyanide when it is not there. Spiking a sample and getting good recovery does not prove that results are accurate. The best way for you to gauge the accuracy of you cyanide methods, or rather, the potential to generate cyanide is to evaluate your methods using the ASTM challenge matrix.

Available cyanide

2011-09-02T20:01:00.001-07:00

I often get questions regarding what cyanide species the available cyanide method is supposed to recover, or worse yet, comments stating that the results of available are supposed to be similar to the WAD and CATC methods but not the same. In actuality, the WAD, CATC, and available methods should recover the exact same species and the obtain the exact same numerical result if there are no interferences present. In the event that the results differ, it should be the available cyanide results analyzed by gas diffusion Amperometry with sulfide abatement reagents that are considered correct. The CATC method and the WAD method should recover the same metal cyanide species in the exact concentration as the available method but don't because the CATC method and the WAD method recoveries vary by metal complex and by concentration. Only OIA-1677 with sulfide abatement quantitatively recovers all metal cyanide complexes without interference. Consider the CATC method again. Did you know hat this method requires chlorination of half the sample? Did you know that the chlorinated half is distilled and the result subtracted from the result obtained by distillation of the non chlorinated half? I assume you recognize that there can be error in a cyanide distillation and analysis, and depending on concentration the difference between two distillations can be fairly high. Let's do a thought experiment. Assume that you have a sample containing 100 ppb of total cyanide (completely complexed with iron). You chlorinate one half and theoretically there should be no reaction. So, theoretically the total cyanide minus the chlorinated cyanide equals zero. Now, let's introduce some error.suppose you get 110 ppb on the total half and 90 ppb on the chlorinated half. Each of these results is within 10% error of the true result, but the subtraction yields 20 ppb CATC. The real answer is zero. Lets reverse it. You get 90 ppb on the total distillation and 110 ppb on the chlorinated distillation. Again, each of these results are within 10% error, but now your result is - 20 ppb. So at 100 ppb total cyanide and staying within 10% error your CATC result can vary between -20 and 20 ppb CN. If your permit limit is 10 or even 20 ppb CATC this is totally unacceptable. And be aware that a 10% error at 100 ppb is not uncommon. Also, be aware that as the concentration decreases the pcecision gets worse. Questionable results such as these are unneccessary. OIA-1677 is approved, and has been for over 10 years, for analysis of available cyanide. This means it is a substitute method if CATC is on your permit. You should go to your regulating authority seeking approval to use OIA-1677. Why would I say this? You have seen how 10% analytical error can cause your results to be off by up to 20 ppb on a sample that did not even contain cyanide. This false reporting of cyanide will not occur with OIA-1677. OIA-1677 measures the same cyanide species that CATC is supposed o measure, but measures them directly with no subtraction. And, with OIA-1677 a 20 ppb detection is huge. I could see a false positive at 0.5 or possibly 1.0 ppb with OIA-1677, but never a false positive higher than 2 ppb. For demonstration, a 2 ppb standard routinely gives us a 10:1 or better signal to noise ratio with relative standard deviations of replicate injections rarely above 5%. this means a 20 ppb concentration is approximately a 100:1 signal to noise and absolutely no chance of being a false positive.

How to sample for cyanide

2011-08-28T10:37:00.000-07:00

Perhaps the more appropriate title should be "How not to sample cyanide" for we have seen that in most cases the way we would normally sample, and preserve a water sample for cyanide analysis is not the way it should be done. So what is it that we normally do, you ask? Well, the normal process is to destroy chlorine with ascorbic acid, add sodium hydroxide to pH 12 and ship it to the lab. Hopefully, your permit does not say 5 ppb.

So, what is the problem you may be asking yourself. I can name you more than one instance where a discharger got fined for cyanide releases that did not really happen; the cyanide was created by preservation and storage. In other words, they did exactly as they were supposed to do. They collected the sample, added NaOH to pH 12, and shipped for analysis. The lab found about 10 ppb total cyanide placing the discharge in violation of it's 5 ppb limit. In searching for the source of the cyanide, the discharger found no evidence that CN should be in their effluent. Not only that, they found if the sample was not preserved to pH 12 and analyzed immediately there was no cyanide, however, if it is preserved and analyzed immediately cyanide is detected. Worse yet, the amount of cyanide detected increases with storage time.

This is an example of cyanide generation. Cyanide is being created by oxidation of nitrogen compounds in the presence of oxidizers. These were disinfected effluents, and even though the disinfectant was theoretically reduced prior to discharge, there is enough remaining to slowly oxidize sample constituents with one of the by products being the cyanide ion.

So the discharger is in the predicament where not preserving the sample gets a non detect keeping them from violating their 5 ppb permit limit, but by not preserving they have violated the permit due to on compliant sampling procedures.

We have been asked why this scenario has not reared it's ugly head in years past and the answer is that no one cared. Only recently have discharge limits been lowered to the extent that 10 ppb total cyanide results in a permit violation.

The easy answer is to not adjust the pH of the sample and/or analyze immediately. This is easier said than done. Immediate analysis is hard depending on location of the effluent, and not all samples retain their original cyanide concentration when the pH is not adjusted. If the samples contain trace metals it is possible that CN be complexed and not fully recovered by the chosen test procedure. The permit holder desiring to not preserve their samples should conduct a holding time study.

So to sample for cyanide, at least in disinfected effluents that may generate cyanide by preservation with NaOH you should consider not adjusting the pH at all. Conduct a holding time study to demonstrate how long a sample can be stored. You must be able to analyze the CN immediately after sampling for the holding time study to be valid. Immediately should be within 15 minutes after the sample was taken. This is hard with most analyzers, however, with an automated method, such as ASTM D7511, it is quite possible. Include multiple replicates of the initial analysis to provide a statistical mean and standard deviation of the original result. Again, hard by most methods, but not by ASTM D7511. After analysis at time zero, store the sample and then analyze each day for up to 14 days. Determine the holding time as the number of days it takes the sample to fall outside of the 95% confidence interval of the original result.

Free Cyanide

2011-08-09T19:01:00.001-07:00

Methods of Analysis for Free Cyanide

EPA believes that measuring free cyanide provides a more scientifically correct basis for establishing criteria for cyanide, however, in 1984 (when criteria was established) there were no EPA approved methods for free cyanide. Since no free cyanide methods were available, EPA recommended measurement of cyanide after a “total” distillation._

Gensemer, Dzombak, and Santore_ analyzed free cyanide by colorimetry without preliminary distillation. The methods, they explain, normally include a key distillation step to remove any interference, however, that distillation can be omitted if the sample contains only simple cyanides in a matrix that is free of interferences. Interferences include sulfide, metals, thiocyanate, a varying pH, and a varying salt content. To accurately measure “ free cyanide” by colorimetry without distillation requires that samples and standards be carefully matched in salinity.

Dzombak, Ghosh, and Wong-Chong_ explicitly discourage the analysis of “free” cyanide by direct colorimetry. They reported grossly inaccurate results for “free” cyanide by direct colorimetry in the analysis of freshwater and seawater samples (Figure 1). The failure of the analysis on both freshwater and seawater samples illustrates that varying salinity produces inaccurate results. Dzombak, Ghosh and Wong-Chong also mention that, though it is feasible to measure free cyanide by Ion Selective Electrode (ISE), it is only accurate in relatively simple, low ionic strength matrices.

Ammonia distillation

2011-08-04T18:52:00.000-07:00

Why do we have to distill ammonia? I assume it dates back to the days when ammonia was determined by either titration or by the Nessler reagent. If you titrate, you have to distill otherwise you would not know what you are titrating. The Nessler reagent doesn't work so well in samples containing salts.

However, if you are determining ammoni with the Berthelot reaction or an ion selective electrode, or especially ion chromatography what, exactly, is the purpose of the distillation?

The Berthelot reaction complexes cations that would precipitate at the high pH necessary for the reaction to proceed and determines ammonia directly in the solution. Is there data anywhere showing that it doesn't work without a preliminary distillation? If there is, couldn't the interference be found and compensated.

The Ion Selective Electrode for ammonia selectively passes ammonia gas through a membrane. What else can pass through at the high pH and cause a reading?

Ion chromatography separates other cations and determines ammonium ion. High concentrations of sodium could interfere, but what about when sodium is not high enough?

Comments?

Total Nitrogen Analysis

2011-08-03T19:16:00.000-07:00

Many people are unaware that TKN is not exactly total nitrogen. The TKN number is the sum of Organic nitrogen and ammonia nitrogen, but excludes nitrogen from nitrate and nitrite. Besides this, not all organic nitrogen compounds are digested by the method. To make matters worse, nitrate interferes causing TKN results to be low when nitrate is present.

The current state of affairs, in the US anyway, requires that total nitrogen be the sum of TKN and nitrate plus nitrite. This is, of course, assuming that your numbers are for CWA reporting. If not you can do one of the heated alkaline Persulfate digestion methods and report that. In clean water samples, the alkaline Persulfate result is the most accurate.

The problem with the alkaline Persulfate method is there is actually no EPA approved method, or even an EPA parameter. This means you must do non peer reviewed manufacturer methods of unknown reliability.

The continuous flow methods using the alkaline Persulfate technique also employ UV irradiation to effect 100% recovery of nitrogen from most water soluble organic compounds. There is really no data indicating what particulate load an automated method can handle before the results begin to be reported low. It is known that a significant portion of organic nitrogen can be bound to particulates. Samples containing particulates should be digested manually with nitrogen determined manually, or by some automated method.

ASTM D7511 Total Cyanide without distillation

2010-12-29T20:17:00.000-08:00

The Method Update Rule proposing the non-distillation UV irradiation gas diffusion Amperometry total cyanide method is now closed from public comment. There will be a period of about eight months as the method, and the rest of the update, goes through the normal process necessary to promulgate a new Clean Water Act method. I have read the docket and saw no negative comments regarding ASTM D7511 or any of the other new cyanide methods. In fact, there were several comments expressing 'pleasure' that some new alternatives for cyanide analysis will finally be approved. It is no longer a question of if ASTM D7511 will be EPA approved for CWA reporting, it is now a question of when. The time-table says August.

The CNSolution is a completely new way of thinking about Cyanide Analysis

2010-10-07T05:48:00.000-07:00

Most people do not know what they want until they actually see it. You do know what you need. You need a faster, more accurate and cost effective means to analyze for cyanide.

The CNSolution
is your answer. It can set you apart allowing you to rise to the top. You have to think differently to buy a cyanide analysis method based on gas diffusion amperometry. You are smarter than others, having examined the data and knowing you are right and other methods are wrong. You are willing to obtain correct results with less labor and in a shorter amount of time. You are a pioneer and desire to get the job done right the first time without pondering meaningless data and mindless repeats. You, and others like you, will change the way cyanide analysis is done. You are the forerunners into a world of accurate cyanide analysis with no distillations and no pyridine. The CNSolution is for you, the visionary.

2008-11-09T17:56:00.000-08:00

Analyze Cyanide Quickly, and Accurately.
Stop wasting time distilling samples and fill your wallet with cash!

“Finally an amazingly simple way to measure cyanide in your laboratory and double or triple profits immediately.”

Are you tired of wasting time and spending money on time-consuming, inaccurate, distillation bottlenecks?

How about sample throughput? Are you sick of your inability to expand because of the extra work from increasing your workload?

Are your clients getting ahead of you, or are they charging less than you and effectively stealing your business because you can’t keep up?

The secret that will save you money is the OI CNSolution. Its unique capability of analyzing for all forms of cyanide without time consuming and costly distillations eliminates distillation and minimizes interferences producing more reliable results and allowing faster turn around times.

Even if Distillation is required, Gas diffusion – amperometry is superior.
The colorimetric methods used in most laboratories require determining total cyanide after distillation by EPA 335.4 or SM4500. The OI CNSolution has been proven more accurate than colorimetric methods.

The low cost of operating the Gas Diffusion - Amperometric FIA instruments allows dischargers to frequently monitor their processes making it possible to quickly detect problems before they can cause serious ecological damage. Routine daily, or even hourly, testing can be realistically implemented so that exact cyanide discharge levels can be accurately known.

The OI CNSolution saves you time.

Aquatic Free Cyanide
Cyanide is about 1000 times more toxic to aquatic life than it is to humans. For this reason, it is important that free cyanide be measured in fragile aqueous environments. Free Cyanide is defined as the amount of HCN that is liberated from a solution at pH 6.0, and should only measure cyanide present in solution as HCN or as CN-.
The OI CNSolution accurately measures aquatic free cyanide by ASTM D7237-06.

The only automated method for free cyanide!

Simple Cyanide Compounds
Simple Cyanides are the readily soluble salts of cyanide such as sodium, potassium, and calcium and along with free cyanide are the only cyanide complexes likely to be present in Drinking Water.
The OI CNSolution accurately measures free cyanide in drinking water by OIA1677-DW or ASTM D6888-04. These flow injection methods are the only interference free approved methods for the determination of cyanide in drinking water that do not require time consuming and expensive preliminary distillations.

Time – consuming distillation is not required!

The OI CNSolution may also be used to accurately measure simple cyanide in milk, assorted beverages, and food extracts.

No distillation required!

Weak and Moderately Strong Metal-Cyanide Complexes
Weak to moderately strong metal-cyanide complexes are compounds that could readily release hydrogen cyanide gas from an acid. Weak Acid Dissociable (WAD), Cyanide Amenable to Chlorination (CATC), and Ligand Exchange methods have been devised in an effort to quantify these complexes.

Do you consistently get false positives or false negatives?
It’s not your fault it’s the methods fault!
CATC and WAD methods, and all distillation colorimetric methods for cyanide are proven inaccurate!

Simply changing your method will solve everything!

The OI CNSolution accurately measures Available Cyanide in wastewater by OIA1677 or ASTM D6888-04, and in ore processing and related metallurgical materials. Gas-diffusion Amperometric flow injection methods are the only interference free approved methods for the determination of available cyanide in wastewater that do not require time consuming and expensive preliminary distillations.

CATC and WAD Cyanide without distillation!
Get results within minutes instead of hours or days!
Increase Capacity up to hundreds of samples per shift!
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Strong Metal - Cyanide Complexes
Commonly known as "total" cyanide and defined by the USEPA as cyanide ion and complexes converted to hydrogen cyanide gas by reflux distillation in the presence of strong acid and the magnesium ion. Methods for the analysis of "total cyanide" include ferrous and ferric complexes along with all other previously mentioned forms. Thiocyanate or cyanate ions are not included.
Colorimetric post distillation OI CNSolution precisely measures cyanide in distilled samples according to EPA 335.4. This flow analysis method is currently the only approved automated, commercially available method for the determination of total cyanide in wastewater samples.

EPA 335.4 and SM 4500 methods are inaccurate!

Years of testing and experiments have demonstrated that distillation and colorimetric methods of cyanide analysis do not accurately yield quantitative, or even qualitative, results in samples with complex matrices.

It has been shown that sulfide interferes significantly. Abundant literature references of efforts to minimize sulfide interference have been found to be ineffective.

The only accurate way to determine post - distillation total cyanide in sulfide bearing samples is to use the OI CNSolution in accordance with ASTM D7284-08.

Distillation is time-consuming and introduces error.

Even with post distillation Gas-Diffusion Amperometric Flow Injection Analysis it is not possible to determine total cyanide in complex samples that contain combinations of, or all of, the following ions; thiosulfate, sulfite, nitrate, nitrite, thiocyanate, and peroxide. The US 40CFR mentions that it is not possible to determine cyanide after distillation from samples containing thiosulfate or sulfite.

Eliminating distillation improves results!

The only method that determines total cyanide in these complex matrices is the Non-distillation OI CNSolution. The UV irradiation gas-diffusion amperometry method uses low temperature, low strength UV technology to selectively disassociate cyanide ions from metal complexes while not allowing the simultaneous destruction or creation of cyanide that is common with high heat distillations.
The OI CNSolution accurately determines true total cyanide rapidly and without distillation.

Total Cyanide Results in minutes, not hours or even days!

Dramatically increase profits – no unnecessary labor costs.
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Sulfate and the CFR

2007-03-18T20:53:00.000-07:00

The EPA has recently published a new Table of approved methods that removes most turbidimetric sulfate methods from the list. This is actually good being that IC is likely the best way to determine sulfate, however, it's quite bad for the thousands of people out there that have found themselves without a method. ASTM D516-02 is your resort as it is equal to the EPA method.

The good thing about this latest publication is that the EPA finally allows laboratory personnel to use their brains and modify methods to get better results. More on this later.

Ammonia

2007-02-12T19:38:00.000-08:00

There is a method much simpler than EPA 350.1 for the determination of ammonia that works quite well on Discrete Analyzers. It is still based on the Berthelot reaction but combines some reagents reducing the number of reagents from four to two. It is faster, and simpler to use plus it doesn't smell as bad. Will it ever be approved?

Ammonia Methods and the Silly EPA

2007-02-10T17:23:00.000-08:00

Methods of analysis for ammonia in soil and water extracts rely, for the most part, on reactions that date bak two centuries. Not that it is bad 'cause if something works it works, but you'd think that in this day of technology it would be allowed by our government to at least take advantage of some new things. Not that we don't take advantage of the instruments that are available since 1830, but we seem stuck to the technology that was established in the Nixon administration. Hello EPA , there is more than one way to skin a cat.

The method most used by environmental labs for the determination of ammonia is EPA method 350.1 based on the Berthelot reaction. In this method, ammonia is converted to chloramine that reacts with phenol under basic conditions to create an intensely blue indophenol dye that's color is directly proportional to the ammonia concentration. The reagents are added together using a segmented flow analyzer (SFA), and mor recently Flow Injection Analyzers (FIA).

Nowadays we have a new analyzer on the scene that is being marketed as a Discrete Analyzer. Where the silliness begins is in the way and order reagents are added because our EPA insists that these Discrete Analyzers duplicate the action of the flow analyzers. The problem is that discrete analyzers are not flow analyzers. The best way to bring about the berthelot reaction is not neccessarily equally and independent of the type of analyzer.

The Analysis of Things

2006-09-09T13:42:00.000-07:00

So often it is expected that a single magical method provided by an instrument manufacturer is going to be the catch all fix to solve all problems. It's funny that for the most part the development done at the manufacturing facility is done by a non-user of the method that does not have a complete grasp of the difficulties that are confronting the average user. Thus, the method is developed on known samples of known interferences and does not, nor cannot, take into account the thousands and thousands of alternate possibilities that the method will later have to deal with.

The laboratory manager, purchasing this method/instrument makes the assumption that the manufacturer is the expert that he is not and relies on this save all method/device assuming all is well in his application. The manager assumes he will not have to think, his lab rats will not have to think, because afterall, someone else did all the thinking for them.

The Discrete Analyzer

2006-03-07T05:23:00.000-08:00

I will be at Pittcon next week standing around in a booth trying to convince people they need to buy our discrete and flow analyzers. Snazzy machines, these are, but they are not the simplistic device that they are portrayed to be. The common misconception is that prestored methods are capable of handling any sample matrix. Again, taking the chemistry out of chemistry. Years ago, like in the 30's. an article called "Chemical Analysis of Things the Way they Are" in this article Hilldebrand (I think it was) discusses his fear that so called rapid chemical determinations (for they are not true analysis) will replace analysis, and the level of skill of the analyst will go down. In this article he discusses the fallacy of assuming that a rapid method designed for one matrix can be applied to all samples with mindless abandon. Thus, we have the environmental testing industry. Our good government has rammed down the throats of the laboratory the legal requirement to analyze contaminants by approved methods regardless of their applicability to the measurement at hand. The typical analyst knows nothing of chemistry, albiet he thinks he does, as he applies untested methods to untested matrices. The consumer (industry) is forced to accept results even if they are wrong, and can be proven wrong, because they are obtained from analysis by approved methods. Thus the cycle continues.

Automated Wet Chemistry

2006-03-05T20:07:00.000-08:00

I know that I am in a narrow field of employment. There are not too many applications in the world, and not too many people understand it. It is difficult to remain in employment in an environment where the supervisors and upper level management do not understand what it is you do and so, therefore, cannot discern truth from un truth. It is easy for them to be fooled by those who talk big and cannot deliver, leaving those who understand the reality of the situation out of the loop. With more than 20 years experience in laboratory analysis, I see myself without the influence that I should have while others who do not have the knowledge are perceived as experts for whatever reason. There are so few of us out there who actually pretend to understand what it is we do, and we are recognized by our willingness to admit we cannot understand it all. So here I sit feeling trapped and doomed.

Cyanide Chemistry

2006-02-19T06:52:00.000-08:00

If I thought Nitrogen chemistry was bad, I should have looked at Cyanide Chemistry first. Cyanide chemistry gets so complex most people just throw up their hands in dispair. This is why OI Analytical offers solutions for analyzing Cyanide other than the EPA's stupidly defined methodology. If you want the right answer, don't follow an EPA method, however, if you don't want a fine you'd better follow the EPA method.

What I am saying is that most EPA methodology for cyanide is severly flawed. For the most part only the OI 1677 method will give yopu a result anywhere near reality.

Nitrogen Chemistry

2006-01-21T12:19:00.000-08:00

The older I get, the less I know I guess. I suppose when I first graduated from college I thought I knew it all, but after years of applications I'm beginning to think I know nothing. Something as seemingly simple as Nitrogen chemistry can get me far more perplexed than it should, or maybe nobody really understands the stuff, they just think they do. I'm sure anybody who has read any of this blog has been able to deduce that my experience is with analytical chemistry. In this field we try to determine the amounts of certain compounds in a certain matrix. Nitrogen compounds can exist many different forms and the attempt to determine each one of them, or to convert all nitrogen into one form for a subsequent measurement is emperical at first glance and then complicated as you dive into it. For years I blindly applied EPA and other "standard" methods without much thought other than this is what is required to do. But now that I am more involved with the development of methods as opposed to just doing them I see that much of the data collected may not really represent what it is supposed to have measured. Besides that, the matrix of the sample itself can greatly influence the ability of the method to analyze that particular form. Even worse, many of the approved methods are actually adding intereferences preventing the method from performing it's best. An example of this dilema that has had me occupied for at least a month is the analysis of Nitrate Nitrogen by its reduction to Nitrite Nitrogen and then a colorimetric method. The reduction of the nitrate to nitrite has to be so precisely controlled that all nitrate is converted to nitrite, but no nitrite is converted to anything else. One method for doing this has been to use hydrazine, but the reaction is so poorly understood I have yet to find an adequate explanation of it in the literature. Basically the literature says "Hey this works" with no real explanation as why. Another commonly used method is the reduction of nitrate with cadmium metal. For this method there is much literary research with experimental results etc, so much so that it is odd that the EPA chose to totally ignore the recommendations of the research.

Colorimetric Methods of Analysis

2005-12-30T16:48:00.000-08:00

I never gave much thought to the actual determinative step in a colorimetric analysis. I supose I either considered it boring or just so well known there was not much point in examining exactly what is going on. I assumed, incorrectly, that a published method was probably all worked out and the chemistry behind each method was fairly well understood. Then it became necessary for e to make adaptations of methods written for one type of instrument and apply it to another. The concept is simple enough, the only problem is.... it doesn't always work. In looking into details as to why it wasn't working I discovered that not only is the chemistry not really known, in some instances what is known seems to be flat out wrong. Hec, for the most part the identity of the colored species is not even known. Analytical chemistry has been blindly applying methodology determined to work but without knowing why for years. In the early days of spectroscopy there was some interest. Nowadays, I guess no one really cares.

NOTES ON METHOD 1677

2005-11-16T15:51:00.000-08:00

NOTES ON METHOD 1677

Federal Register: July 7, 1998 (Volume 63, Number 129)Page 36809-36824

Method OIA-1677 is actually the first Cyanide method available that can be defined in terms of the cyanide species being measured because it recovers cyanide completely throughout the analytical range of the Method (2 g/L to 5000 g/L) from the following cyano-species:
HCN,           CN-,
[Zn(CN)4]2-, [Cd(CN)4]2-,
[Cu(CN)4]3-, [Ag(CN)2]-,
[Ni(CN)4]2-, [Hg(CN)4]2-
and Hg(CN)2.

In addition, the recoveries are concentration independent, which is not the case with either the CATC or WAD procedures.

Method OIA-1677 demonstrates greater specificity for cyanide for matrices in which interferences have been encountered using CATC methods. In addition, Method OIA-1677 measures cyanide at lower concentrations and offers improved precision and accuracy over currently approved CATC methods. Method OIA-1677 also offers improved laboratory safety and reduces laboratory waste compared to currently approved CATC methods. This significantly reduces the generation of hazardous waste by the laboratory. Cyanide analysis by Method OIA-1677 is also more rapid than by currently approved methods.

Analysis Time

    The reflux distillation procedure required by CATC methods, including setup and measurement, takes approximately two hours to perform. Therefore, determination of CATC takes approximately four hours of analysis time. In contrast, Method OIA-1677 takes approximately two minutes to perform. This difference is especially significant for laboratories performing many CATC analyses.

Cyanide - Definitions

    Cyanides are, as a class, one of the toxic pollutants pursuant to section 307(a)(1) of CWA (see the list of toxic pollutants at 40 CFR
401.15). Total cyanide is a priority pollutant as derived from the toxic pollutant list (see 40 CFR Part 423, Appendix A).
    In the context of analytical methods, cyanide or cyanides refers to the group of simple and complex chemical compounds that can be determined as cyanide. Cyanides are of the form A(CN)x where A is an alkali such as sodium or potassium, or a metal such as calcium, and x is the number of CN groups attached to A. Cyanides are present in aqueous solutions as CN- and as hydrocyanic acid (HCN or hydrogen cyanide). The proportion of CN- and HCN in solution is dependent on the pH and the dissociation constant for HCN. At low pH, the cyanide exits as HCN; at high pH, it exists as CN- at the near-neutral or slightly acidic pH of most natural waters, nearly all cyanide is present as HCN.
Most of the metal cyanides are insoluble or only slightly soluble in water but may form a variety of soluble cyanide complexes when a cyanide complex such as potassium or sodium cyanide is present.
    Hydrogen cyanide is the cyanide species most toxic to aquatic life.
The toxicity of the other cyanides is attributable to the degree of their dissociation and conversion to HCN. Some cyano-metal complexes, such as those of zinc and cadmium, dissociate almost totally (i.e., a knowledge of the complex can be used to determine the amount of cyanide). Other cyano-metal complexes, such as those of iron, dissociate little. For these complexes, a large amount can be present without cyanide being detected. Still, other complexes, such as mercury, nickel, and silver, dissociate partially and only under certain conditions. For complexes that release some, but not all, of the cyanide ion, the amount of dissociation must be known to determine the amount of cyanide. This total, partial, or near lack of dissociation presents a difficulty in the determination of cyanides, as explained below.

There are numerous interference problems when the currently approved methods were used to test certain sample matrices and therefore there was a need for a cyanide method that reduces or eliminates these interferences. A method for measuring available cyanide by flow injection analysis (FIA) was developed by ALPKEM in cooperation with the University of Nevada at Reno, Mackay School of Mines in 1995. Besides overcoming most matrix effect problems, Method OIA-1677 uses amperometry as an innovative technology to improve the detection of available cyanide. Method OIA-1677 is faster, more accurate and precise, and allows determination of available cyanide at lower concentrations than other currently approved methods. Method OIA-1677 is also safer because it requires a smaller amount of a potentially hazardous sample, requires less manual operations where accidents could lead to exposure, and uses less hazardous substances in the sample preparation and determinative steps.

Methods for Determination of Cyanide

    Methods presently approved at 40 CFR Part 136 measure cyanide in two ways: as ``total cyanide'' and ``cyanide amenable to chlorination''
(CATC). A third way is as ``weak-acid dissociable'' (WAD) cyanide. Methods for determination of total cyanide attempt to measure all cyanide species that may dissociate in the environment over time and when exposed to natural forces (e.g., heat, light, water of varying hardness, pH) but ultimately fail to do so because many species cannot be dissociated completely under normal laboratory conditions. The CATC and WAD methods, and Method OIA-1677, which employs ligand exchange, all attempt to measure ``available'' cyanide, i.e., cyanide species that dissociate in the presence of chlorine and/or acid. The species of cyanide measured by these methods are cyanide ion (CN-) hydrogen cyanide (HCN), and the cyano-complexes of zinc, copper, cadmium, mercury, nickel, and silver. The net result is that the WAD, CATC, and OIA-1677 methods all measure nearly the same species of cyanide. The term “available cyanide” is used in Method OIA-1677 because the chlorination reaction used in the CATC methods is not employed, although the cyanides determined are the same.
    Methods for total cyanide employ reflux distillation in the presence of sulfuric acid and magnesium chloride to dissociate CN- from cyanide-metal complexes. This process is more vigorous than the dissociation processes used in the WAD, CATC, and ligand-exchange methods, and a greater number of cyanide species are dissociated in the distillation process. The HCN liberated during the distillation is captured in an aqueous solution of sodium hydroxide and the cyanide in the solution is determined spectrophotometrically or titrimetrically.
    Cyanide amenable to chlorination (CATC) is determined by chlorinating the available cyanide in the sample using calcium= hypochlorite (Ca(OCl)2 measuring the HCN using the total procedure, and finding the CATC concentration by difference between the total cyanide measured before and after the chlorination.
    Available cyanide is determined in Method OIA-1677 by flow injection, ligand exchange, and amperometric detection. The ligand- exchange reagents displace cyanide from cyano-metal complexes. Further details of Method OIA-1677 are given in a description of the method.
    As stated above, no method measures all species of cyanides because several species (such as cobalt and gold cyanides) are so stable that they are either not dissociated or are only slightly dissociated in the reflux distillation or chlorination processes. Method OIA-1677 and CATC methods measure easily dissociable and partially dissociable species.
Most notable among the partially dissociable species are the certain cyanides of nickel, mercury, and silver when these cyanides are present at high concentrations (ca 2 mg/L). These cyanides are recovered in the range of 55--85 percent in the CATC methods. In contrast, these species are recovered completely in Method OIA-1677, and this is the significant difference between the performance of Method OIA-1677 and approved methods for CATC. As a result, if a sample contains high concentrations of certain cyanides of nickel, mercury, or silver, the result will be somewhat higher when Method OIA-1677 is used, provided no interferences are present. At concentrations below approximately 0.2 mg/L, the recoveries of these cyanides from CATC methods and Method
OIA-1677 are all approximately equivalent and near 100 percent.

Effect of Interferences on Cyanide Methods

    The CATC determination is highly susceptible to interferences, as many substances other than cyanides can react in the chlorination process. For an overview of the nature and magnitude of these interferences, see the paper [[Page 36812]] presented by Goldberg, et. al. at the Seventeenth Annual EPA Conference on Analysis of Pollutants in the Environment, May 3-5, 1994 (available from the EPA Sample Control Center, 300 N. Lee Street, Alexandria, VA 22314 (703-519-1140). Interferences in the CATC determination may be by thiocyanate (SCN-), sulfide (S-2 >), carbonates, nitrite, oxidants, bisulfite, formaldehyde (HCHO), surfactants, and metals. Method OIA-1677 is either not susceptible to these interferences or contains procedures that eliminate these interferences or mitigate their effects. The reason that this method is much less susceptible to interferences than the approved CATC methods is that neither the chlorination reaction nor distillation is employed. Rather, the aqueous sample passes a gas diffusion membrane through which the HCN diffuses. EPA believes that most of the reported interference problems in the determination of cyanide are overcome using Method 1677.
    Interferences in the CATC methods normally produce an inflated result for cyanide and, in many instances, the measured level exceeds the concentration for total cyanide, potentially providing a more controversial result in some regulatory contexts. Because Method OIA-
1677 is nearly immune to the interferences that inflate results from
CATC methods, the result of an analysis using Method OIA-1677 will nearly always be lower, and therefore closer to the true value for cyanide than a result from an analysis using a CATC method. The only exception may be for an analysis in which interferences are not present but certain cyanides of nickel, mercury, or silver are present at high concentrations, as described above. Therefore, the tradeoff in use of
Method OIA-1677 versus presently approved CATC methods is that, with
Method OIA-1677, there is a reduced susceptibility to interferences, whereas with approved CATC methods, there is a somewhat decreased result if certain cyanides of nickel, mercury, or silver are present at high concentrations. EPA believes that the tradeoff heavily favors use of Method OIA-1677 based on the expected susceptibility of CATC methods to interferences combined with the small probability that a cyanide of nickel, mercury, and silver will be present at a high concentration and be the dominant cyanide in a given discharge. Dominance is important because if a cyanide of nickel, mercury, or silver is present at a concentration that is small in comparison to another cyanide present, the effect on the measured cyanide concentration will be diminished in proportion to the concentration relative to the other cyanide.
    Because the lowest result for a given cyanide determination can be produced by either Method OIA-1677 or by a presently approved CATC method, dischargers will likely choose the method that produces the lowest result. The adverse environmental impact to choosing presently approved CATC methods is that not all of the nickel, mercury, or silver cyanide will be recovered (and measured), if any of these cyanides are present.

There may be interferences from volatile organic compounds or a sulfur containing or other inorganic gases. If the electrochemistry at the silver working electrode and the volatility of certain organic species are examined, some interference from organic species could be encountered. For examples, acetonitrile (CH3CN) could possibly pass through the membrane and would almost certainly aid the oxidation of silver at the working potential, producing an analytical signal; low molecular weight aliphatic mercaptans might also pass through the membrane and be active at the working electrode.

Method OIA-1677 is less susceptible to interferences than other methods for available cyanide, including CATC and WAD methods. Therefore, Method OIA-1677 will not subject dischargers to violations for those instances in which an interference with a CATC or WAD method would inflate a cyanide concentration above a permit limit. Any method that is less susceptible to interferences and thereby comes closer to determining the true value of a pollutant will improve the quality of analytical data.

Comparison of Method OIA-1677 to Current Methods

    Methods currently approved for determination of available cyanide all test for CATC. Although they represent the best methods available to date, these methods are prone to matrix interference problems. Method OIA-1677 to be a significant addition to the suite of analytical testing procedures for available cyanide because it (1) has greater specificity for cyanide in matrices where interferences have been encountered using currently approved methods, (2) has improved precision and accuracy compared to currently approved CATC cyanide methods, (3) measures available cyanide at lower concentrations, (4) offers improved analyst safety, (5) shortens sample analysis time, and (6) reduces laboratory waste.

    Method OIA-1677 is not subject to interferences from most organic species. The flow-injection technique of Method OIA-1677 excludes all interferences, except sulfide and sulfur compounds that are volatile in acid solution. Sulfide is eliminated by treating the sample with lead carbonate and removing the insoluble lead sulfide by filtration prior to introduction of the sample to the amperometric cell used for cyanide detection, or by using the alternate lead abatement reagent.

    Method OIA-1677 was tested against two existing cyanide methods:
Method 335.1, an EPA-approved CATC method, and Standard Method (SM) 4500 CN I, a weak-acid dissociable (WAD) cyanide method. Comparative recovery and precision data were generated from simple metallo-cyanide species in reagent water. Recovery and precision of each method was comparable for the easily dissociable cyanide species. Method OIA-1677 showed superior precision and recoveries of mercury cyanide complexes.
    While Method 335.1 does not specify a method detection limit, colorimetric detection is ``sensitive'' to approximately 5 ug/L. The method detection limit (MDL; described at 40 CFR part 136, Appendix B) is 0.5 ug/L for Method OIA-1677, as determined in a multi-laboratory study.

    Method OIA-1677 offers improved analyst safety for two reasons. The first reason centers on the generation of hydrogen cyanide gas, a highly toxic compound. Although the proposed flow-injection analysis
(FIA) method and currently approved CATC methods all generate HCN, the currently approved methods generate a larger quantity of gas during distillation in an open distillation system. As such, extra care must be taken to prevent accidental release of HCN into the laboratory atmosphere. Method OIA-1677, because it tests a much smaller sample, generates significantly less HCN. In addition, the gas is contained in a closed system with little possibility for release. The second reason for improved safety centers on the use of hazardous substances.
Currently approved CATC methods require use of hazardous substances in the distillation and color developing processes. These hazardous substances include hydrochloric acid, pyridine, barbituric acid, chloramine-T, and pyrazolone. Method OIA-1677 requires only hydrochloric acid at a much lower concentration than is used in CATC procedures.
    Method OIA-1677 offers a reduced analysis time that should increase sample throughput in the laboratory. Method OIA-1677 uses an automated mixing of the sample with hydrochloric acid and exposure to the gas diffusion membrane in order for the sample concentration to be determined. This process takes approximately two minutes per sample. As a comparison, Method 335.1 requires a one-hour distillation procedure plus the time necessary to add and develop the sample color to determine the presence of cyanide.
    Less laboratory waste is generated in Method 1667 because it requires a much smaller sample size for testing. Method 335.1 requires handling a sample size of 500 mL for distillation. Method OIA-1677 requires the addition of the ligand exchange reagents to 100 mL of sample, from which 40-250 uL is used for analysis. This reduces the amount of both hazardous sample and toxic reagents that must be handled and subsequently disposed.

Quality Control

    The quality control (QC) in Method OIA-1677 is more extensive than the QC in other approved methods for CATC. Method OIA-1677 contains all of the standardized QC tests proposed in EPA's streamlining initiative (62 FR 14976) and used in the 40 CFR part 136, Appendix A methods. An initial demonstration of laboratory capability is required and consists of: (1) An MDL study to demonstrate that the laboratory is able to achieve the MDL and minimum level of quantification (ML) specified in Method OIA-1677; and (2) an initial precision and recovery
(IPR) test, consisting of the analysis of four reagent water samples spiked with the reference standard, to demonstrate the laboratory's ability to generate acceptable precision and recovery. An important component of these and other QC tests required in Method OIA-1677 is the use of mercuric cyanide as the reference standard for spiking. Mercuric cyanide was chosen because it is fully recovered in Method OIA-1677 and weak-acid dissociable (WAD) methods, whereas mercuric cyanide is only partially recovered in the CATC method. Therefore, mercuric cyanide demonstrates the ability of the ligand-exchange reagents to liberate cyanide from moderately strong metal-cyano complexes. Method OIA-1677 requires the use of standards of known composition and purity, which facilitates more accurate determination of recovery and precision and minimizes variability that may be introduced from spiking substances of unknown or indeterminate purity.


Validation of the Method OIA-1677

    ALPKEM developed Method OIA-1677 according to procedures set forth in EPA's Guide to Method Flexibility and Approval of EPA Water Methods (EPA-821-D-96-004, December 1996), which is available from the EPA's Water Resource Center (phone: 202-260-7786).

Intralaboratory Validation Study Results

    Prior to interlaboratory testing, ALPKEM conducted a single- laboratory validation study both to refine the method and to demonstrate the method's specificity and selectivity.
    The single-laboratory study consisted of three sets of tests to establish (1) the ability of Method OIA-1677 to identify the various species of ``free'' metallo-cyanide complexes, (2) the ability of
Method OIA-1677 to identify cyanide in the presence of interferences, and (3) the recovery and precision of Method OIA-1677 compared to EPA
Method 335.1 and SM 4500 CN-I. To determine Method OIA-1677's identification of ``free'' metallo-cyanide complexes, two different concentrations of 11 different metallo-cyanide complexes were each analyzed individually in triplicate, for a total of 66 analyses. Method
OIA-1677 yielded recoveries ranging from 97 to 104 percent for six of the eleven complexes (cadmium, copper, mercury, nickel, silver, and zinc). However, as with the currently approved methods for available cyanide, Method OIA-1677 did not determine cyanide in iron, gold, and cobalt cyanide complexes.
    To test the ability of Method OIA-1677's to identify cyanide in the presence of other species, two different concentrations of 11 interferents were analyzed in triplicate for a single cyanide test solution, resulting in a second set of 66 analyses. Even in the presence of these interferents, cyanide recoveries ranged from 99 to
103 percent.
    To compare the performance of Method OIA-1677 to the performance of approved methods, 2 different concentrations of the same 11 ``free'' metallo-cyanide complexes given above were analyzed individually in triplicate by the EPA-approved CATC Method 335.1, SM 4500 CN-I, and
Method OIA-1677. This resulted in a third set of 66 data points. These results show improved recoveries and reduced relative standard deviations for Method OIA-1677 compared to both the SM 4500 CN-I and the CATC methods for selected analytes. For the mercury cyanide complexes, recovery improved from 59 percent for SM 4500 CN-I to 99 percent for Method OIA-1677. High levels of interferences in the nickel and silver determinations showed similar improvements over the CATC method. However, data for zinc, cadmium, and copper were comparable among the three cyanide procedures. There was no recovery and thus no method improvement for cobalt, gold, or iron cyanide complexes.

Interlaboratory Validation Study Results

    In association with the Analytical Methods Staff (AMS) in EPA's
Office of Water, ALPKEM conducted an interlaboratory validation study.
Those study results, briefly described here, are detailed in a report titled, The Interlaboratory Validation of Method OIA-1677. The purpose of the interlaboratory study was (1) to confirm the performance of Method OIA-1677 in multiple laboratories, (2) to assess Method OIA-1677 interlaboratory data variability, and (3) to develop Method OIA-1677 QC acceptance criteria.
    Nine laboratories participated in the interlaboratory method validation study, working cooperatively as the WAD Cyanide Round Robin
Group. Each laboratory analyzed an identical set of nine field samples using Method OIA-1677. These field samples were collected from nine different effluents ranging from a publicly owned treatment works (POTW) to an industry likely to contain cyanide in its effluent. Each sample was analyzed in triplicate using the FIA procedure for a total of 243 analyses (9 laboratories  x  9 samples in triplicate).
    Along with the analysis of the field samples, each laboratory performed all required QC analyses, including initial calibration, calibration verification, determination of initial precision and recovery, blank analysis, determination of ongoing precision and recovery (OPR), determination of matrix spike recovery and matrix spike duplicate recovery (MS/MSD) in each sample type, assessment of recovery of cyanide as Hg (CN)2 spiked into samples (ligand-exchange reagent performance check or LERPC). In addition, each laboratory performed an MDL study.
    The relative standard deviation (RSD) of results across all laboratories and all samples was 12 percent. The mean sample recoveries across all effluent types tested was 96 percent, and the MS and MSD mean recoveries were 99 percent across all effluent types tested. These results exceed generally accepted norms for analytical chemistry results.
    Prior to collection of interlaboratory data, one study participant submitted comments that focused on the difficulty in addition of the proper amounts of WAD A & WAD B ligand-exchange reagents to a sample.
The difficulty occurred because of the variability of drop size. The method was modified to designate a specific volume of ligand-exchange reagent rather than a certain number of drops. The modified method was distributed to interlaboratory study participants prior to testing.

Excerpted from: www.epa.govfedrgstr/EPA-WATER/1999/December/Day-30/w33627.htm

Phosphate Chemistry

2005-11-16T15:43:00.000-08:00

Phosphate Chemistry

When phosphoric acid is dissolved in solution, the following equilibria are established among the four species H3PO4 (phosphoric acid itself), H2PO4-1 (dihydrogen phosphate anion), HPO4-2 (hydrogen phosphate anion), and PO4-3 (phosphate anion).

Phosphate in Water

Phosphorous occurs in water as phosphates and are classified as soluble orthophosphate, polyphosphates, and organic phosphates. Sources of phosphate in water include natural weathering but also industrial processes because phosphorous is a major ingredient of many soaps and surfactants. Also, phosphorous is used extensively in fertilizers because it is an essential nutrient for plant growth.

Only orthophosphate is measured by the molybdenum blue method. All other forms of phosphorous must first be digested and converted to orthophosphate prior to measurement. The various digestion procedures allow an empirical separation of phosphorous according to its chemical form. Because only phosphate responds to the molybdenum blue method it is termed “reactive phosphorous” and all reactive phosphorous measured is assumed to be phosphate. A weak acid digestion, termed hydrolysis, converts polyphosphates to orthophosphate. Acid Hydrolysable phosphorous is thus a mixture of the existing orthophosphate and any polyphosphates. A stronger acid digestion using oxidizers to destroy organic matter converts organic phosphorous to phosphate and at the same time dissolves inorganic phosphate that is bound to sediment. Phosphate measurement from this strong acid digestion is termed “Total Phosphorous”. Total phosphorous results include orthophosphates, polyphosphates, bound inorganic phosphate, and organic phosphorous.

Orthophosphate as Molybdenum Blue (Molybdate Reactive Phosphorous)

Molybdenum blue is formed by the reduction of phosphomolybdic acid and its formation is dependent upon pH, molybdate concentration, temperature, acid concentration, and time. The optimum acid concentration for proper color development of molybdenum blue is about 0.4N in the sample at the time of measurement. At this pH all forms of soluble phosphorous exist as H3PO4. The H3PO4 reacts with Molybdate and a reducing agent to form the Molybdenum Blue compound.

The optimum molybdate concentration is determined by the [H(]/[Mo+6] ratio and should be approximately 74. Multiply the grams of Ammonium Molybdate by 0.0049 to obtain [Mo+6] in the color reagent and then calculate [Mo+6] in the final solution. Then divide the final Normality of the acid reagent by the final Molarity of the Molybdenum. If this ratio is not correct it is possible to obtain either no blue color at all, or a blue color from the reagents alone.

Increased temperature will speed the reaction causing the blue color to stabilize faster. This blue color formed is not stable and its stability depends upon the reducing agent used. Normally for greatest accuracy, measurements of the blue color must be taken within a well-defined time window.

SOP's

2005-11-03T19:56:00.000-08:00

Well, anyway, it appears that even the regulators who inspect laboratories expecting them to follow EPA SOP's expect SOP's to be written for them. I never imagined that a procedure written by an instrument manufacturer would be followed word for word. Isn't it necessary for each laboratory to adapt the procedure to the peculularities of his own laboratory? How can the instrument manufacturer forsee all the variety of analytical ranges desired and all the different matrices to test and then come up with one generic method that works for all? This is what I have been saying about the loss of the art of chemical analysis. It is expected that machines are so smart that people will not have to think anymore.

Writing SOP's

2005-10-24T16:03:00.000-07:00

Does anybody think it would be worthwhile to have a business writing SOP's and training laboratory personnel to use them? I have been told this is in demand.

The importance of the analyst

2005-10-20T14:37:00.000-07:00

There is no way that the perfect instrument that always gets the right result will ever be invented. There is no way thet the right results will ever be obtained without a qualified analyst at least overseeing the analyses. Even as there is more instrumentation making things appear simpler, without qualified analysts the results are still useless.

Ease of Instrumentation...more on it

2005-09-26T05:18:00.000-07:00

But, can an instrument be created so simple that the analyst does not even need to think? The real question is are the samples so similar that an instrument (or test) can be designed well suited for all without any adaptation. The answer, for environmental testing, is no! It is not possible to create methodology that will be suitable for all samples because the variety of environmental samples varies too much. Even water, which one might think is all the same, has extreme varieties in its matrix.

Ease of Instrumentation

2005-04-17T13:50:00.000-07:00

As instrumentation becomes more popular the required education level of a chemical analysis technician goes down. At least, that is, in the eyes of the laboratory manager. The instrument manufacturer is thus challenged with making instrumentation and methodology easy to use. While chemical analysis was once a craft, now it expected to be a process similar to an assembly line manufacturing widgets. The line of instrumentation that I work with, is even now, so variable that there are numerous ways to obtain a system that gives the same results, but the technique is considered mature to the point that there is very little modern literature about it. Never was there an established guideline for it to follow, and in the days of interest all literature involved example after example of different ways to do the same thing. That was when the analyst was a craftsman, and the analysis was a craft. Now it is expected to be a black box with sample in and number out.

The methods, must therefore, be easy and instrument easy to maintain. There must be written rules and written guidelines to follow. There must be a defined right way to do things.

Good Luck.