Determination of sulfide in the leather industry by capillary electrophoresis

Capillary electrophoresis (CE) was investigated for the determination of sulfide in effluents and waste water samples from the leather industry. A 10 mM sodium sulfate electrolyte at pH 10.5 was used and a quaternary ammonium hydroxide was added for the reversal of the electroosmotic flow (EOF). The linearity, separation efficiency and the effects of pH, concentration of the EOF modifier and the capillary dimensions were investigated. Direct UV detection at 229 nm provided the best specificity and also the best sensitivity, The limits of detection were 41 and 10 mu g of S2-/l using a 75- and a 100-mu m I.D. capillary, respectively. The reproducibility was considerably improved by using the internal standard technique. Molybdate, iodide and biphthalate may be used as internal standards. Spiking of real samples gave recoveries between 102 and 111%. The CE method presented here was compared with the classical methods and it was concluded that it may be a good alternative for determining sulfide in difficult samples.