It is not possible to reproduce water determination in DMSO because it alters the stoichiometry of the KF reaction. This shortcoming becomes even greater as the number of samples increases.
We tested the water content in different DMSO sample quantities alone and added to a defined amount of water by volumetry and coulometry. The findings obtained from these two methods were comparable.
The problem was picked up again in a series of subsequent tests. We ascertained that it is also impossible to perform indirect determination in a KF oven.
As a result of the various facts, the recommendation must be made that no more than 1 mL of DMSO should be analyzed. The injection of several samples in a coulometric cell should be avoided. Addition of a 1000 ppm standard shows the current effect on the titration vessel.
Download the full Laboratory Report for dimethyl sulfoxide (DMSO) (L 141) here