Abstract
A sensitive and selective capillary electrophoresis method with indirect UV-detection employing a high-sensitivity cell of special design was used for the determination of sulphide in the presence of sulphate in drinking and wastewaters. The running buffer consisted of chromate, tetradecyltrimethylammonium hydroxide, glutathione and polethylene glycol at pH 10.0. The use of a high-sensitivity cell and the addition of polyethylene glycol were the key factors of improving sensitivity and selectivity of the proposed method. The method was proved suitable for its intended use by applying the procedure starting from the calibration of the CE instrument to validation of all experimental parameters. The resolution factor between sulphide and sulphate under optimal conditions was found to be about 2.0. The limits of detection (LODs) of sulphide and sulphate were 2.0 and 0.3 ng/mL, respectively. Analysis of standard mixtures of sulphide and sulphate gave good linearity in the ranges of 5.0–500.0 and 2.0–160.0 ng/mL, respectively, with correlation coefficients ranging between 0.994 and 0.996 at 95% confidence level. Application of the proposed method to the analysis of water was successfully achieved and statistically confirmed. It is important to note that in drinking water ultra trace concentrations of sulphide ions were successfully detected by the current method.