The use of tristimulus colorimetry for the determination of hydrogen cyanide in air by a modified König method

Abstract

A simple visual and tristimulus colorimetric method (threedimensional system CIE-L*a*b*) for the determination of trace amounts of hydrogen cyanide in air has been developed. The method is based on the suction of hydrogen cyanide through a chlorinating cartridge where cyanogen chloride is formed, which is further driven to an indicator disc made of a modified cotton fabric. This indicator disc is placed into an adapter. Prior to analysis, the disc is saturated with a chromogenic reagent, a solution of 5,5-dimethyl-1,3-cyclohexanedione (dimedone) and 4-benzylpyridine in ethanol. In the presence of hydrogen cyanide (cyanogen chloride), a pink coloration emerges on the indicator disc, the intensity of which is evaluated either visually or by use of a tristimulus colorimeter. The detection limit is 0.1 mg m-3. The method is mainly suitable for mobile field analyses. It was applied for the CHP-5 chemical agent detector introduced into the equipment of the Czech Army corps.