Flow injection analysis of sulfide by gas phase molecular absorption UV/Vis spectrometry

A simple FIA method is described for the determination of sulfide in aqueous solution. Two hundred and thirty microliters of sulfide sample solution is injected into the water stream. The stream is then mixed and reacted with a carrier solution containing sulfuric acid. The hydrogen sulfide evolved is separated from liquid stream by the use of a gas-liquid separator and then is swept into a flow-through cell using N-2 carrier gas. The absorbance of the gaseous phase is measured at 195 nm by the use of an UV/Vis spectrophotometer. Under optimum conditions, the limit of detection was 0.07 mug S2-. The relative standard deviation of repeated measurement of 23 mug of S2- was 0.4%. Up to 60 samples h(-1) can be analyzed. The effects of several anions and cations on the determination of sulfide were studied. The proposed method was successfully applied to the determination of sulfide in sulfurous spring water samples and the results obtained were in good agreement with the results of stabilized iodine titration procedure.