To quantify metals in biological samples, we tried to find good conditions for wet-digested mineralization of the samples and for separation of metal ions in chromatography. A 500μl volume of aliquot was transferred to a glass tube, and was evapolated at 100°C for 2 hours. A 5.5 ml volume of a mixture of concentrated nitric acid-70 % perchloric acid (10 : 1, v/v) was added and heated, consecutively, at 80°C for 12 hours, at 140°C for 2 hours, at 180°C for 2 hours, and finally at 190°C for 1 hour to evapolate the residual acids. After addition of 500 μl of 10 mM nitric acid, the metals were extracted by a suspension mixer (32 r.p.m., 1 hour). One hundred μl of the extracted solution was applied to the chromatographic system : cation-exchange column, TSKgel IC-Cation SW (Tosoh Co.) ; eluent, 0.35 M lactic acid-0.35 M sodium lactate (pH 3.0) ; flow rate, 0.7 ml/minute ; column temperature, 30°C. After adding a color-forming reagent (100 mg/l 4-(2-pyridylazo)-resorcinol in 40 g/l Na
2CO
3 ; flow rate, 0.7ml/minuie) to the effluent, five different metal ions of Cd
2+, Co
2+, Cu
2+, Ni
2+ and Zn
2+ were detected at 520 nm. The peaks were separated in approximately 25 minutes, and were quantified even at the 1-10 ppb levels. The present procedures were considered to provide simultaneous detection and accurate quantitation of the above five metals in the biological samples.
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