A simple in situ visual and tristimulus colorimetric method for the determination of diphosgene in air

Abstract

A simple visual and tristimulus colorimetric method (three-dimensional system CIE-L*a*b*) for the determination of trace amounts of diphosgene in air has been developed. The method is based on the suction of diphosgene vapors through a modified cotton fabric filter fixed in a special adapter. Prior to analysis, the filter is saturated with a chromogenic reagent based on 4-(p- nitrobenzyl)pyridine. The optimal composition of the reagent is 2 g of 4-(p-nitrobenzyl)pyridine and 4 g of N-phenylbenzylamine in 100 ml of a 50:50 ethanol-glycerol mixture. The intensity of the formed red coloration of the filter is evaluated visually or by a tristimulus colorimeter (LMG 173, Lange, Germany). The detection limit is 0.01 mg m-3. Acetyl chloride and benzoyl chloride react in 150 and 50 times higher concentrations, respectively. The method is suitable for mobile field analysis. .