Coulometric Karl Fischer Determination

With the coulometric method, iodine is generated directly in the titration vessel by anodic oxidation of iodide caused by electrical pulses emitted from an iodine generator.

The Mettler DL37 Coulometer produced by Mettler Toledo, Inc., Highstown, N.J. is a Karl Fischer instrument that utilizes coulumetric moisture determination. It has a measurement range from 10mg to 100mg water content per sample with a detection limit of 0.1mg water. This model is capable of accurately determining moisture content down to parts per million.

This type of instrument offers advantages for measurements on relatively dry products. For example, the pharmaceutical industry is interested in measuring the moisture content in pharmaceuticals which contain less than 1% moisture. However, because iodine is generated at a relatively slow rate, it would take a long time to measure samples with higher moisture using coulometric determination.