Simultaneous determination of sulphide and sulphite by gas-phase molecular absorption spectrometry. Comparative study of different calculation methods

A method for the simultaneous determination of sulphide and sulphite is described, which involves continuous H 2S and SO 2 generation, preconcentration in a liquid nitrogen trap and measurement of the molecular absorption spectra of volatiles in the gas phase in 190–220 nm range. Under the recommended conditions (sample flow: 50 ml/min and concentrated sulphuric acid flow: 12 ml/min; generation time: 4 min) linear response ranges from 0.05 μg/ml for S 2− and 0.20 μg/ml SO 2− 3 are obtained with detection limits of 0.05 and 0.20 μg/ml respectively. Synthetic mixtures of the two components have been solved and a comparative study of different calculation methods has been made. In conclusion, multiwavelength methods offer better precision and accuracy.