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Novel methods to determine sulfide in aqueous samples by quantification of lead sulfide spots

Two new, simple, accurate, and economical methods to find out sulfide (S2−) at low levels (10−9 g) in aqueous samples have been proposed. The first method involved the generation of hydrogen sulfide (H2S) in a specially designed small cell by interacting sulfide solution with hydrochloric acid. The resulting H2S is passed through a filter paper pre-dipped in lead acetate solution that made dark brown lead sulfide spots on the paper. In the second method, micro-liter drops of sulfide solution are applied on silica gel TLC pre-moistened with the lead acetate solution that developed lead sulfide spots. The color densities of the spots were calculated by scanning the spotted paper and TLC and analyzing the image using a specially developed software. The TLC method was more effective at trace levels having a linear response in the range 5–100 ng in comparison to 100–900 ng of the H2S method. Statistical examination of the calibration line validated the pertinence of these methods for the analysis of reduced form of sulfur in aqueous samples, particularly when dealing with small sample volumes.