DIRECT DETERMINATION OF SELENIUM IN HUMAN BLOOD-SERUM AND PLASMA BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

A method is described for the direct determination of selenium in seru m or plasma by electrothermal atomic absorption spectrometry with deut erium-arc background correction. Samples are diluted (1 + 2) with a mo difier containing palladium nitrate and Triton X-100. Samples are atom ised from a L'vov platform in a pyrolytically-coated electrographite t ube and peak area signals are measured. Direct determination is possib le by using selenium standards matched to the physiological concentrat ions of sodium chloride, calcium and phosphate. The detection limit is 6 mu g/L in the original sample. Precision at a selenium concentratio n of 97 mu g/L was 2.2% RSD within batch and 3.0% RSD between batch. A ccuracy is shown by (i) analysis of a Seronorm reference serum (value obtained 97 +/- 3 mu g/L; recommended value 96 mu g/L); (ii) recovery of added selenium (93.3 +/- 6.7% and 98.2 +/- 3.3% at additions of 30 and 60 mu g/L, respectively) and (iii) comparison of results with mean of all laboratories in an external quality assessment scheme.