Direct analysis of mercury in Traditional Chinese Medicines using thermolysis coupled with on-line atomic absorption spectrometry

The purpose of this study is to develop and apply a mercury analyzer system capable of quantitative analysis of mercury in Traditional Chinese Medicines (TCM) drugs in the concentrations range from ng g⁻¹ to mg g⁻¹. No sample pre-treatment was needed and this greatly simplifies the analytical procedure and minimizes potential sources of contamination. The precisions of analyzing solid mercury standard sample and real TCM materials were 2.1% and 2.5-8.2%, respectively; and the recovery based on the analysis of standard reference materials ranged from 95.2% to 105%. The performance of the method has been compared with inductively coupled plasma-mass spectrometry (ICP-MS) technique and excellent agreements were observed between the two methods. The method has been applied to the investigation of Hg content in several TCM drugs containing or not containing cinnabar. Mercury concentration in the same TCM products differs widely with different manufacturers, suggesting that external contamination and the Hg presence in raw herbal materials are the main sources of Hg. In addition, comparison of mercury thermal releasing profiles between TCM drug and cinnabar suggests that mercury conversion from cinnabar to biological matrices-bound Hg could occur because of the aid of other ingredients in the formulated drug.