Short Communication Simple in situ Visual and Tristimulus Colorimetric Determination of Sulfur Dioxide in Air

A simple in situ visual and tristimulus colorimetric method of determination of the trace amount of sulfur dioxide in air has been developed. Tristimulus colorimetry is based on application of three-dimensional colour space L*a*b * according to CIE (Commission Internationale de l'Éclairage). L * represents lightness and a * and b * represent chromaticity. The analytical method is based on drawing the harmful pollutants through a filter made of modified cotton fabric, which is planted on a special extension piece. The filter is saturated with chromogenic reagent based on 5,5'-dithio-bis(2-nitrobenzoic acid) in the mixture of N,N-dimethylformamide dimethyl sulfoxide (1: 1). On the filter the orange colour appears; the intensity of the colour is assessed visually and/or by a tristimulus colorimeter (LMG 173, Lange, Germany). The detection limit is 0.01 mg.m-3. Interferences of reduction (especially hydrogen sulfide), oxidation, alkaline and acid agents have been describes