ASTM E203

Water Using Volumetric Karl Fischer Titration

Applicability: Applies to most solid or liquid organic and inorganic compounds in which free water or water of hydration is to be determined, accommodating both pyridine-based and pyridine-free Karl Fischer reagents. Suitable for water concentrations from parts per million up to essentially pure water; samples with very low water content (≤500 mg/kg) are more accurately addressed by the coulometric Karl Fischer variant (ASTM E1064). Gaseous samples at ambient temperature are excluded from this method’s scope.

Purpose: Determines water content by dissolving or dispersing the sample in a suitable solvent and titrating with a standardized Karl Fischer reagent to a potentiometric endpoint detected automatically, with a visual endpoint method provided as an appendix option. The Karl Fischer reaction selectively consumes water in proportion to the volume of reagent delivered, providing a direct gravimetric-equivalent measure of moisture content. Results are widely used in pharmaceutical, petrochemical, food, polymer, and specialty chemical industries to control moisture for product quality, stability, and regulatory compliance.