DETERMINATION OF SELENIUM IN HUMAN HAIR AND NAIL BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

A microwave digestion procedure was used to prepare samples for determination of total Se by electrothermal atomic absorption spectrometry (ETAAS) with palladium modification. Conversion of organoselenium compounds to inorganic selenium was achieved by heating 100 mg hair with 0.5 ml concentrated nitric acid for 1 min and then, after the addition of 0.5 ml hydrogen peroxide (30 vols.), reheating for a further 8 min. The accuracy of the method was confirmed by analysis of certified hair reference materials containing 2.00 and 0.58 mu g g(-1) Se. The detection limit is 0.02 mu g g(-1) Se. A variation of the procedure was used to analyse nail samples. Digestion was achieved by heating 100 mg of nail with 1 ml nitric acid for 2 min and, after the addition of 1 ml hydrogen peroxide, for a further 33 (3 x 11) min. The detection limit for this procedure is 0.03 mu g g(-1) Se. Analysis of hair reference materials and both hair and nail samples by neutron activation analysis and ETAAS showed reasonable agreement between the techniques. The ETAAS procedure is more rapid and convenient. Analysis of 25 hair samples gave a range of 0.31-0.76 mu g g(-1) Se (mean value 0.52 +/- 0.11 mu g g(-1)) and for 27 nail samples a range of 0.17-0.66 mu g g(-1) Se (mean value 0.46 +/- 0.16 mu g g(-1)) was obtained.