Analytical Sciences

Determination of Trace Water in Gas Samples by an Improved Karl Fischer Coulometer

Huiru DONG, Pengyu BI, Jianping CAO, and Shouyong ZHAO

College of Science, Beijing University of Chemical Technology, Beijing 100029, Peoples Republic of China

The determination of trace water in gas samples, such as isobutene, chloromethane (polymeric staple gases) and SF₆ by a conventional Karl Fischer coulometer is very difficult, because of the adsorption of trace water on the surface of sample pipe, the gasification of the liquefied samples, and the migration of moisture into the measuring cell from the surroundings. To solve these problems, we improved a device for coulometric determination of water by Karl Fischer method. The improved coulometer was used to determine the trace water in isobutene, chloromethane and SF₆; RSD was less than 5%, and recoveries ranged from 94.1 to 109.1%, which is adequate for the analysis of industry.

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