Simple in situ Visual and Tristimulus Colorimetric Determination of Sulfur Dioxide in Air
Abstract
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 threedimensional colour space L*a*b* according to CIE (Commission Internationale de l'clairage). 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'-dithiobis(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.
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