Some operators use Karl Fischer water standards daily while others do so sparingly. Regardless of the type of operator you are, there still seems to be some confusion about what Karl Fischer water standards are supposed to accomplish and/or why we use them.

Water standards for Coulometric Karl Fischer Titrators verify “recovery” of a known amount of water. We say “recovery” because we are seeking to recover or measure water that was introduced during a test. When introducing a water standard with a known amount of water using a syringe and needle — known as the direct injection method — we should expect to recover all of that water. If we do not recover it all, there could be a problem.

Water standards can also be used to verify recovery for Volumetric Karl Fischer Titrators, but they can also be used to help calculate the titer value associated with Volumetric Titration. Additionally, if a solids evaporator oven is being utilized in conjunction with a Karl Fischer Titrator, we can use a water standard in powder form to verify moisture delivery from the evaporator to the titrator.

We offer a line of Hydranal Water Standards covering a range of moisture content for both direct injection tests as well as evaporator powder standards.

Typically, the high range standard known as “10.0” is used with the Volumetric Karl Fischer Titrators. The other lower range water standards including the “1.0”, “0.1” and “Water Standard Oil”, are used with the Coulometric Karl Fischer Titrators. You can see a breakdown of the water standards as follows:

· “10.0” contains 10.0mg (10,000 micro grams) of H20 per gram (1g = 1mL)
· “1.0” contains 1.0mg (1,000 micro grams) of H20 per gram (1g=1mL)
· “0.1” contains 0.1mg (100 micro grams) of H20 per gram (1g=1.16mL*)
· “Water standard oil” contains a target PPM result (by LOT) of 6.0PPM
· “Water standard KF oven” (230°-240° C) approximate 5.55% result
· “Water standard KF oven” (140°-160° C) approximate 5.0% result

Note that a water standard with a specific gravity of 1.0 means that 1gram (mass) is equal to 1 milliliter (volume). You will notice that the “0.1” water standard has a specific gravity of less than 1.0 because it contains some xylene (we will cover specific gravity in more detail later).

To actually run a direct injection water standard test the operator will typically fill their syringe with 4 mL of water standard (water standards are generally sold in convenient 4mL ampules) and dispose of 1 mL to clean and prep the needle prior to conducting a direct injection water standard check. Utilizing the 3 mL remaining inside the syringe, three separate tests can be performed by injecting 1mL for each subsequent test. If the operator finds the results to be inconsistent, a larger amount of water standard can be used for each injection to improve accuracy and repeatability.

Hopefully this information will help with some of the challenges many operators encounter daily as well as improve performance and reliability of moisture testing results.  If you feel you can benefit from further assistance click on this link to request a consultation with one of our Karl Fisher experts: [Request Consultation]

We will cover more regarding Karl Fischer Titration including using specific gravity, trouble shooting problems, volumetric reagents and calculating sample sizes to name a few. Until then, we hope you will continue to read, enjoy and share our posts regarding the interesting and sometimes confusing topic of Karl Fischer Titration.

Thanks for reading and, as always, feedback is welcome.

Hank Levi

We all know that surface tension affects our daily lives thru everyday applications like the ink you use in a pen, detergents for washing clothes, soap to clean your hands, paint for the house, just to name a few.  But Surface tension is more involved in your life than you may think.
Tap water is usually around 72 to 73 dynes/cm.  This can vary by temperature and other variables but for the sake of this blog post we will assume 73 dynes/cm.  Now this is where it gets interesting.  At 73 dynes/cm water will hydrate you.  Or does it?  You see, It is known that on a cellular level your body has to convert fluids to 45 dynes/cm to allow the water to penetrate the human cells.  Once water penetrates the cells it can hydrate and remove toxins from the cells.   If water cannot effectively penetrate human cells an accumulation can build up and over time cause the cells to die.  Amazingly, I have seen places around the world where people claim to have special water.  They claim their water has a lower surface tension and less colloidal minerals.  You knew this was coming..Yes, these same people have demonstrated good health as they easily live to be 100 years old!  And yes, they attribute this to their water.

Not surprisingly, I see web sites now that sell supplements to lower the surface tension of  water to improve your health.

Fact or Fiction you ask?
I think I am going to order some of these supplements and check it myself with a digital tensiometer!  As they say the proof is in the pudding. Or in this case the surface tension!

Stay tuned.  I will update my findings and how I did.

Thank You,
Gus

Novice: “Hi, I need to test for moisture and I need a Karl Fisher Titrator.  Can you tell me how much it costs?”

Expert: “O.K., do you need a Coulometric or Volumetric Karl Fisher Titrator?”

Novice: “uh what?”

Expert: “Well you see there are two kinds of Karl Fisher Titrators.  Depending on your sample size and the amount of moisture you expect to find -it may not only be advantageous but necessary to use a Coulometric vs. a Volumetric..and or vice versa.”

Novice: “I see.”  So how do I know what kind of Karl Fisher I need?

Expert: “Generally speaking, if you are working with small samples (0 to a few grams) AND the expected moisture is low (around 1% or less) you probably want to use a Coulometric Karl Fisher.  On the other hand, if your sample size is larger AND you expect to find a lot of moisture in the 2%+ range then you probably should consider a Volumetric Karl Fisher Titrator.”

Novice: “Do they both report moisture results the same way? You know, accuracy, resolution, repeatability?”

Expert: “Yes they do.  Both Volumetric and Coulometric Karl Fisher Titrators report moisture results in either Parts Per Million (PPM) or %.

Novice: “So then what makes them different?”

Expert: “Coulomeric Karl Fisher Titrators use a reagent called an Anolyte.  This Anolyte is 100% self contained and requires only an electrical current to cause a reaction where the Anolyte releases iodine.  It is this “iodine” that “neutralizes” the moisture inside the vessel.  A typical Coulometric Karl Fisher Titration Vessel can hold about 75mL of Anolyte.  The amount of Anolyte inside the vessel can only “release” so much iodine and therefore can only neutralize and measure a finite amount of moisture.  In this case using the 75mL as the example the reagent can only neutralize and measure 750,000 micro grams of moisture (water/H2O).  Now compare this to a Volumetric Karl Fisher and the game changes.  The Volumetric Karl Fisher method does not use a single self-contained Anolyte reagent that reacts to an electrical current.  Instead, the Volumetric titration is performed by “dripping” in IODINE at an precise amount into the titration vessel where there is a SOLVENT solution present in the vessel.

Novice: “How does the Volumetric Titrator “Drip in” IODINE into the vessel where the SOLVENT is located?”

Expert:”Good question.  It uses a buret that has a piston that moves up and down pulling The IODINE solution from a source bottle into and filling the buret and then pushing it out through tubing and into the vessel. ”

Novice: “Is there another name for this “IODINE solution”?  How do I get it?

Expert: “Another good question.  “This IODINE solution” is what makes the volumetric method so versatile when measuring larger amounts of moisture via Karl Fisher Titration.  The Iodine solution can come in two forms and with differing strengths.”

Novice:” Two forms?  Different strengths? Huh?

Expert: ” Yes, the two forms are referred to as “One-Component” and “Two-Component”.”

Expert: “The “One-Component” Iodine solution is referred to as Composite or Titer.  The Composite can come in 3 strengths; 1 (1mL of composition can consume 1mg or 1,000micro grams of water), 2 (1mL of composition can consume 2mg or 2,000micro grams of water) and 5 (1mL of composition can consume 5mg or 5,000micro grams of water).  We refer to these compositions as Composition-1 (aka Comp1), Composition-2 (aka Comp2), and Composition-5 (aka Comp5).

Novice: Differing Strengths.  Hmmm.  So for every 1mL you “drip in” it will consume, neutralize and measure the corresponding amount of moisture depending on the Composition strength.

Expert: “That’s right.  So for example if you use a Volumetric Karl Fisher Titrator with a 20mL buret you could conceivably introduce in one push of the piston that’s inside the buret, 20mLs of Composition.  If your using Comp5 you would be able to consume, neutralize and measure 20mL x 5,000 micro grams =100,000 micro grams of water.   Most Composition are sold in 500mL bottles.  So each bottle has the capacity to consume, neutralize and measure 2,500,000 micro grams of water.

Novice: “That’s a lot of water measuring capability!”

Expert: “Yes it is.”

This is a simple example and there are other factors to be considered for sure.  We thought this brief example would help those just getting started and trying to understand the basic comparison between Coulometic Karl Fisher and Volumetric Karl Fisher.

I suppose the refractometer market is kind of like the cell phone industry but with fewer manufacturers. I guess I’m glad then to see that Atago has not taken it’s foot off the accelerator when it comes to improving their products. Take the newest RX-5000i digital benchtop refractometer. It does not cost any more than the previous models, the RX5000alpha and the RX5000plus. Huh? Why? I think Atago wants to stay ahead of the competition by delivering a better product. So the new RX-5000i (and 5000iPlus) Digital Benchtop refractometers now have an improved user interface that incorporates a touch screen with seemingly easier navigation and operation. We will have to see how customers respond to this and let everyone know once the units have been out for awhile. Still, I do think the improved temperature range and the delay as well as the USB interface will be well received by customers.

You might be thinking, so what. I would probably agree with you but have you seen the news recently about oil spills? How about the one that just happened in the Gulf of Mexico? Since oil is less dense than water it floats. Look out Florida, Alabama, Mississippi, Louisiana, and Texas!

Liquids have different densities and will not mix if the difference in densities is great enough. Temperature is an important factor that can affect a liquids density too. In general, as liquid temperature increases, density decreases.

As you might expect knowing the density of a liquid serves numerous purposes and can provide valuable information for making decisions. Density can tell you how much sugar is in a can of soda, or how much gasoline and kerosene is in a petroleum product, or even aid someone in predicting how two or more liquids will interact. Understanding what density is, what affects density, and how density affects other physical properties is also important in using and translating this information into an everyday useful tool.

We live in a physical world and so it would make sense that we would want to be able to define these physical properties around us. Having a way to define these physical properties is helpful to those who need to use the information.
• How much space does it take up?
• How heavy is it?
• How much of this can we put into that?
• What is it?
• Many everyday products are packaged by volume but sold by weight
• Fluid properties; predictive correlations can be made if you know the density
• If we change some of the ingredients that make up the fluid property will it change the weight?

The neat thing about understanding liquid density is that it can answer not only the three basic questions; What is the mass (weight) of the liquid?, what is the volume of the liquid? What is the density of the liquid? But also, what is the liquid? Yes, we can actually compare liquids to grade and categorize them using a term known as specific gravity.
If you found this interesting stop back again as we explore further…

First, make sure your analytical balance or specific gravity calculation is not the problem. Next, focus your attention on the reagents. Reagents can cause problems if they are not being replaced often enough. With a dual-reagent setup the operator places anolyte into the main vessel (anywhere from 75mL to 150mL of anolyte solution) depending on the vessel size, and catholyte into the generator electrode (5mL of catholyte solution).

Now for some reason, most operators focus their attention primarily on the anolyte reagent and take great care in monitoring the condition and level of the anolyte. Unfortunately their is a tendency to forget about the catholyte. I say unfortunately because it is this oversight that can cause the problem.

Before I tell you the reason for the problem it’s helpful to know some useful information about the reagents ability to measure moisture. A typical vessel can hold 100mL of anolyte. 100mL of anolyte (Coulomat A, Coulomat AG, Coulomat AG-H) can measure 1,000,000 micro grams of water. Yes, 1 million micrograms of water!. Conversely, the pre-measured 5mL ampules of catholyte solution (Coulomat CG)that goes into the generator electrode has the ability to only measure 300,000 micro grams of water

Do you see it? Do you see the connection?

There is a 3 to 1 relationship of the catholyte to anolyte! …roughly..

Yes, you should be replacing the catholyte 3 times per 1 charge of the vessel. Or put another way, change the catholyte 3 times as often as you change the anolyte.

Now, back to the problem and the answer. If your not replacing the catholyte often enough it will actually begin to convert itself into a salt by-product. This “salt by-product” can then become deposited down around the frit at the bottom of the generator electrode (AKA inner buret) and clog the receptors. When this happens the generator electrode does not work as effectively and can cause low recovery on expected moisture levels.

So please make sure to change the catholyte more often and if you haven’t already done it you can soak your generator electrode in methanol or even a light acid over night to clean out some of those salty deposits. That should help.

In this last picture we show a Karl Fisher Vessel with a Single Reagent Generator Electrode. Notice how there in no frit at the bottom? All you see is the platinum screen. Just thought it would be nice to show both and the differences.

(Note: Coulomat AK anolyte and Coulomat CG-K catholyte are used in combination for samples with Keytones and have a 1 to 1 relationship and can measure 100,000 micrograms of water. Also, the popular Coulomat Oil anolyte has a smaller amount of moisture measuring capability as compared with the other mentioned anolytes above and has a capacity to measure 300,000 micrograms of moisture. eg. If your using Coulomat oil anolyte and Coulomat CG both have the capacity to measure 300,000 micro grams of water and have a 1 to 1 relationship.

Hope this helps.

We have found that a number of Aquapal III users have been operating the Karl Fisher titrator without the seals that go with the caps on the vessel. If the seals are not used excessive ambient moisture can seep into the top of the vessel (headspace). If this is happening you may be seeing longer pre-conditioning times, higher drift values and higher reagent use.
We just want to remind the operators of the Aquapal III about the importance of this issue and that using the seals should be included in your every day use.  You may want to double check.
If you have any questions on this subject or have other technical concerns please contact us via email or give us a call.
I hope you find this information helpful.

Scientificgear co-hosts hospitality suite on Monday, June 15, 2009 for members and attendees.

Providing testing equipment and technical support for common petroleum tests including Total Acid Number (TAN), Total Base Number (TBN), Bromine Number, Mercaptan and H2S as well as moisture measurement using karl fisher titration.