Rapid determination of heavy metals and arsenic in herbal medicines using energy-dispersive X-ray fluorescence spectrometry.

The Heavy Metals Limit Test in the Japanese Pharmacopoeia is a chemical method used to detect the total amount of heavy metals based on Pb contents. However, determining the amounts of particular metals has become popular since the ICH-Q3D Guideline for Elemental Impurities was adopted. This is effectively performed using energy-dispersive X-ray fluorescence (EDXRF) analysis, an analytical method used to detect elements. In this study, we determined six elements (Cr, Cu, As, Cd, Hg, and Pb) in 25 herbal medicines using EDXRF and compared the quantitative values to those obtained using inductively coupled plasma-mass spectrometry (ICP-MS). The 25 herbal medicines used included 20 plants, two animals, and three minerals. EDXRF quantitative values for Cr, Cu, As, and Pb were obtained through calibration curve methods, whereas Cd and Hg were all below the limit of quantitation (10σ). Comparison of the quantitative values obtained via EDXRF and ICP-MS revealed ratios of 65-198%. The results for both methods were similar, with slightly larger differences observed for minerals between the EDXRF and ICP-MS quantitative values than those observed for plants. Some differences in quantitative values were observed in the comparison of six herbal medicines among different collection sites, owing to the environments in which Coptis rhizome and Mentha herb were grown. Furthermore, Longgu revealed significant elemental variations among the samples during simultaneous multi-elemental analysis. EDXRF enabled the easy and convenient determination of heavy metals in herbal medicines. Thus, it has potential applications in the quality control and evaluation of herbal medicines.