Tips for moisture measurement using Karl Fischer titration

Karl Fischer titration  is an analytical technique used to quantify a sample's water content using a highly selective chemical reaction. First popularised in the mid-20th century, Karl Fischer titration has become widely applied in the quality control of petroleum, industrial chemicals, pharmaceuticals, and the like. It is also used in the R&D of substances related to the development of new materials and energy alternatives.

In Karl Fischer titration, water is extracted from a sample preparation and measured after a subsequent chemical reaction. Samples, whether in liquid, gas, powder, or pellet form, are all easy to measure with high precision. However, caution must be observed for both the pH of the Karl Fischer reaction, and for the use of samples containing substances known to interfere with it.

The ideal pH range to conduct Karl Fischer reactions is pH5.5 to pH8. The lower the pH, the slower the reaction proceeds, whereas reactions performed at too high a pH tend to generate side reactions. Measurement in both situations invites the possibility of significant measurement errors. KEM suggest adding neutralising agents such as imidazole and salicylic acid to highly acidic and highly basic samples respectively, making sure to adjust the pH of the sample-containing Karl Fischer reagent in the measurement cell.

False positive errors may occur with samples containing ketones because they produce water after reacting with alcohols such as methanol present in some Karl Fischer reagents, so please use a Karl Fischer reagent designed for use with ketones.

With analysis requiring chemical reactions, it is crucial to know the chemical composition and characteristics of your sample in advance. If you have questions regarding Karl Fischer moisture titration, please contact KEM's friendly consultants.

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