DETERMINATION OF SELENIUM IN BIOLOGICAL SAMPLES BY HYDRIDE GENERATION AAS AFTER COMBUSTION IN HIGH-PRESSURE OXYGEN

A simple and accurate method for the determination of selenium in biological samples was investigated by the combustion of samples under a high pressure of oxygen followed by the hydride generation atomic absorption spectrometry. The accurately weighed ground sample less than 1 g is ignited in a Parr 1108 oxygen combustion bomb filled with oxygen to 3 MPa and added with 1 cm3 of water. Ignition normally takes about 1/2s. The selenium trioxide formed dissolves in water as SeO(4)2-, which is in turn reduced to SeO(3)2- by being boiled in 6 mol dm-3 hydrochloric acid medium for 3 min. After diluting the above solution to 100 cm3 with water, atomic absorption measurement is carried out by using the hydride generation system and quartz cell which is heated in an acetylene-air flame according to the instrumental conditions given in Table 1. The optimum concentrations of sodium tetrahydroborate and hydrochloric acid to produce hydrogen selenide are 0.5% (0.05% NaOH) and above 3.5%, respectively. The method of standard additions was employed to determine selenium contents in natural samples. For NBS Bovine Liver 1577 and 1577 a, selenium contents of 1.09-mu-g g-1 and 0.66-mu-g g-1 were in good agreement with certified values of (1.1+/-0.1)-mu-g g-1 and (0.71 +/- 0.07)-mu-g g-1, respectively. Selenium contents in some other samples, NIES Mussel and soybeans, were also in good agreement with those obtained by neutron activation analysis as shown in Table 3.