Moisture Analysis…To Karl Fischer, or not to Karl Fischer
The determination of water content (moisture) is one of the most frequently done tests in Laboratories today. It is performed on solids, liquids, fuels, biomass, foods, plants, soils, or just about any substance you can think of. The importance of knowing water content can range from helpful information to critical. Two methods most widely used today are
1. Drying methods can be simple and economical, since all that is needed is a balance, calibrated oven, and timer. They may be suitable for solids that have water as their only volatile component, which can also be easily released by heating. Unfortunately, there are several disadvantages to these methods:
2. Titration methods (Karl Fischer analyses) are very specific, actually measuring the water content of the sample directly. The advantages are numerous:
The simplified chemistry of Karl Fischer is that free Iodine is introduced into the cell with the sample, and combines with water stoichiometrically to a certain endpoint.
Volumetric titration uses a very accurate burette to dispense the Iodine reagent.
Coulometric titration generates free Iodine out of the electrolyte in the cell itself.
Most matrix issues (i.e. side reactions, solubility) with solid or liquid samples can be solved with the proper sample preparation and/or treatment. It is very important to know the sample matrix whenever possible, to produce good results.
Proper sampling technique plays a critical role in the relevance of the results:
When in doubt about sampling, containers, or suitability of the method, always play it safe and contact the chemists at the lab. Sterling Analytical can handle a variety of Karl Fischer applications.
Karl Fischer analysis is the most versatile technique for moisture content for the widest variety of applications, as long as it’s done properly.
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