DIRECT DETERMINATION OF COBALT AND NICKEL IN POWDERED BIOLOGICAL SAMPLES BY GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY

A concentration procedure was developed for the direct determination of cobalt and nickel at sub-ppm levels in biological samples by Zeeman atomic absorption spectrometry (Z-AAS), because the sensitivity of Z-AAS is at mu-g/g level for these elements even if the solid sampling technique is applied. For this purpose, biological samples were ashed by a muffle electrothermal furnace before the atomic absorption measurement, because the masses of biological samples are at least reduced to less than one fifth when they are ashed in the electrothermal furnace. The concentration factors of 5-50 were obtained for the biological samples. The concentration factors depend on the total amounts of Na, K, Mg and Ca.