A continuous flow vapor generation system for the determination of sulfide at low levels in aqueous samples ‎based on hydrogen sulfide prevaporation and spectrophotometric detection has been developed. In a ‎modified commercial vapor generator, the analyte was converted into hydrogen sulfide by reaction with ‎hydrochloric acid, separated in a gas liquid separator and accepted into a dilute alkaline solution, thus, ‎interferences could be avoided. Subsequently, the solution acidified and merged with N,N-dimethyl-p-‎phenylenediamine (DMPD) and Fe (III) to produce methylene blue dye. The absorbance was measured at 668 ‎nm after 10 min. The effects of parameters on the detection system such as concentrations of acid, DMPD, and Fe ‎‎(III) were studied. The influences of experimental operating parameters including concentration of ‎hydrochloric acid, volume and concentration of trapping solution, flow rates of solutions and Ar carrier gas, ‎magnet stirring rate in trap vial and generation time were evaluated and optimum conditions were obtained. ‎Under the operating conditions, the proposed method provides a linear working range of 2-100 ng mL-1 sulfide ‎with a relative standard deviation of 3.8% (RSD, n = 7) at 50 ng mL-1 S2- and a detection limit (3a, n = 7) of 1.7 ng ‎mL-1 S2-. The proposed technique for separation, preconcentration and detection was applied satisfactorily to ‎sulfide determination in spiked contaminated tap water.‎

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