Indirect Determination of Mercury in Traditional Chinese Medicine by Flame Atomic Absorption Spectrometry

An indirect determination method based on ultrasonic irradiation is proposed for oxidation of the elemental copper into copper (II) ions by mercury (II) ions and subsequent determination by flame atomic absorption spectrometry. In the advanced oxidation process, complete reduce of mercury ion can be accomplished within 5 min under the condition of ultrasonic irradiation in an acetate-buffer solution (pH=5), thus the mercury can be determined with the absorbance of copper (II) formed by flame atomic absorption spectrometry. The operating conditions for the oxidation of the elemental copper into copper (II) ions by mercury (II) ions were investigated, and the interferences from various ions were evaluated. Under the optimized conditions, the calibration curve was linear up to 0.8 μg ml^-1 Hg. A detection limit of 6 ng ml^-1 Hg and a relative standard deviation of 2.1% for 0.2 μg ml1 Hg were obtained. The accuracy of method was verified by the determination of mercury in the certified reference human hair. The method was successfully applied to determination of soluble mercury in traditional Chinese medicine.