DETERMINATION OF TOTAL SELENIUM IN WATER BY ATOMIC-ABSORPTION SPECTROMETRY AFTER HYDRIDE GENERATION AND PRECONCENTRATION IN A COLD TRAP SYSTEM

A cold trap system for the determination of selenium by hydride generation-atomic absorption spectrometry (HG-AAS) is described. For a 30-ml sample the limit of detection is < 2 ng/l. and the precision is better than 4% at the 30 ng/l. level. A number of digestion procedures for the destruction of organic matter prior to the determination of total dissolved selenium in water has been tested and compared. Concordant results were obtained except for oxidation by peroxodisulphate in strongly acidic solutions with a high content of organic material. The selenium concentrations found were in agreement with those obtained by HG AAS after preconcentration by evaporation and dry ashing with the magnesium nitrate-nitric acid-hydrochloric acid method.