Determination of the water content in tablets by automated Karl Fischer titration

Huvuddokument

The water content of tablets determines the release of their active ingredients as well as their chemical, physical, microbial and shelf-life properties. Accordingly, the water content is of crucial importance and has to be accurately determined. This paper describes the straightforward determination of the water content using automated volumetric Karl Fischer titration (KFT). Tedious sample preparation steps are eliminated by using a high-frequency homogenizer that additionally serves as a stirrer. Prior to titration, the homogenizer comminutes the tablets directly in the KF solution. As the comminution process takes place directly in the hermetically sealed titration vessels, interference from atmospheric humidity does not occur. Even after 24 h in the vessels, the moisture content of four different tablet type samples was within 93…108% of the initially determined values. With a coefficient of determination of 0.99993 the KF method is highly linear for water amounts between 4 and 215 mg. For all investigated tablet types, KFT provides results that lie within the range expected by the manufacturer.