Determination of trace levels of cobalt in silicate rock samples by graphite furnace AAS and comparison with ICP-AES and microwave induced plasma MS

Abstract

A convenient analytical method for the determination of trace amounts of cobalt in geological samples was investigated by atomic absorption spectrometry (AAS) equipped with a pyro-graphite furnace. In order to obtain accurate analytical results, two methods of preparing calibration curves, the standard addition method and the matrix matching method, were examined in detail by using the standard geological samples issued from the Geological Survey of Japan (GSJ ; JA-1, JA-3, JG-3 and JG-1a). The analytical results obtained by AAS were ascertained by using an inductively coupled plasma atomic emission spectrometry (ICP-AES) equipped with an ultrasonic nebulizer and microwave induced nitrogen plasma mass spectrometry (MIP-MS). The proposed method was applied to the determination of cobalt at 1μg/g levels in geological samples which will be certified by the Korea Institute of Energy and Resources (KIER; KG-1 and KG-2). The detection limit (three times of relative standard deviation of blank) for cobalt was 5.3μg/l when 10μl of solution was measured. The precision for the deter-mination (relative standard deviation at 5 determinations) of cobalt was 0.4-3.4% when standard geological samples were analyzed.