Karl Fischer / Water Analysis

The Karl Fischer Titration is a titration method for measuring water content in basically all types of substances. It was invented in 1935 by the German chemist Karl Fischer. The Karl Fischer Titration is based on an iodine / iodid reaction: The water reacts with iodine. The endpoint of the titration is reached when all the water is consumed. The process uses an organic base (B), sulphur dioxide, iodine and an alcohol. The original Karl Fischer method used pyridine as organic base and methanol as alcohol. Since then the reagents have been improved. Nowadays Karl Fischer reagents are available which are less toxic (no more pyridine but imidazole as organic base, ethanol instead of methanol) and which provide a faster reaction. During the titration, iodine is added to sample and the amount of iodine used to consume all the water contained in the sample is measured. There are two possibilities to add the iodide to the sample. In the so called Volumetric Karl Fischer Titration, a solution with an exactly known concentration of iodine is added to sample by means of an electric burette. The amount of iodine added to the sample is calculated from the volume of iodine solution used. In the Coulometric Karl Fischer Titration the iodine is electrolytically generated. The amount of idodine added to the sample is determined by measuring the current needed for the electrochemical generation of the iodine. When reacting with water, the brown iodine is reduced to the colourless iodide. The Hybrid Karl Fischer titration is the most advanced and at the same time the most versatile technique for Karl Fischer moisture titrations. It is basically a combination of both, the coulometric and the volumetric method: The iodine is electrolytically generated and –if the moisture content of the sample exceeds a certain level – a solution with an exactly know concentration of iodine is added at the same time. The Water Testing Laboratory performs drinking water testing as required and assists in ensuring safe drinking and source waters by testing samples provided Environmental Health Department in support of Public Health regulations. The Water Testing Laboratory also assists other organizations and agencies with monitoring projects requiring accurate microbiological testing, so that the organizations may comply with regulations and improve water quality. Water testing includes trace analysis capabilities. Intertek water analysis capabilities vary by location, please contact Intertek to determine the laboratory best suited to your water testing requirements.