NICKEL AND STRONTIUM NITRATES AS MODIFIER FOR THE DETERMINATION OF SELENIUM IN URINE BY ZEEMAN PLATFORM GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY

A mixture of nickel and strontium nitrates has been proved to be suita ble and feasible for the determination of selenium in urine by graphit e-furnace atomic absorption spectrometry with respect to the thermal s tabilization and minimization of urine matrix interferences. Thermal p retreatment temperature of 1400 degrees C and 900 degrees C can be uti lized in aqueous standard solution and 1:3 diluted urine with the prop osed modifier, respectively. The results demonstrate that nickel and s trontium nitrate mixed modifier can significantly remove or depress tr oublesome interference caused by sulfate, phosphate and concomitant me tal ions. The graphite furnace temperature program and modifier mass h ave been optimized. The amount of mixed modifier required for stabiliz ing selenium and suppressing the effect of urine matrix is markedly lo wer than those documented in the literature, which reduces the risk of graphite furnace contamination. The effects of different atomizer sur faces on the selenium sensitivity were compared in this work. Better r ecoveries were obtained for different urine samples in the presence of nickel and strontium nitrates.