Indirect AFS Determination of Copper in Chinese Herbal Medicines after Extraction with iso-Pentanol

A method for indirect determination of copper in Chinese herbal medicines by AFS was proposed in this paper. In a weakly acidic solution. CuI was reacted with HgI42- to form stable Cu2HgI4 precipitate, which was extracted with iso-pentanol. Mercury in organic phase was determined by AFS, and the amount of Hg found was converted into contents of copper in sample. Linear relationship between values of fluorescence intensity and mass concentration of copper was obtained in the range of 0.01-0.1 mg·L-1, with detection limit (3S/N) of 3.5 μg·L-1. The proposed method was used in the analysis of 3 CRM′s, i.e., astragalus root (GSB-19), tea (GSB-7) and orange leaf (GSB-11), giving results in consistency with the certified values. Values of RSD′s (n=9) found were in the range of 0.8%-2.4%.