SIMULTANEOUS DETERMINATION OF SULFIDE AND SULFITE 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 H2S and SO2 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 mu g/ml for S2- and 0.20 mu g/ml for SO32- are obtained with detection limits of 0.05 and 0.20 mu g/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.