The Scientific*gear Blog

A Word About Karl Fischer Water Standards

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 Karl Fischer 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. 

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

Most people know about Karl Fisher as a method for determining moisture content.  After that there seems to be confusion when the words “Coulometric” and “Volumetric” are mentioned.  It goes something like this:

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.