Traditional medicines based on herbal products and extracts play an ever increasing role around the world. The chemical composition of Traditional Chinese Medicine (TCM) herbs is commonly studied from the viewpoint of toxicity and bio-availability.
All medicinal products for human and animal use must meet proven quality, safety, and efficacy. However, the quality assurance of herbal medicinal products can be problematic because of the many unidentified chemical entities in the finished products.
A suitable technique for the determination of heavy metal and other element impurities is ICP-MS. It was therefore just included in the new version of the Chinese Pharmacopoeia for the determination of Pb, Cd, As and Hg. The main principle of the technique is explained in the figure.
In a study, the reliability of both the ICP-MS hardware and USEPA Method 200.8 were evaluated for the determination of a range of elements in TCM, using an Agilent 7500 ICP-MS instrument. The study clearly demonstrated the suitability of ICP-MS for the determination of trace and major elements in various digested CRMs (Certified Reference Materials) and its applicability to the analysis of TCM. Several Certified Reference Materials (CRM), including both key trace elements such as As, Pb, Hg, Cd, and major components such as P, Ca, Fe, K, and Na, were digested and measured using the Agilent ICP-MS instrument during method evaluation.
However, for full coverage of key elements in TCM, a collision/reaction cell ICP-MS is necessary to remove molecular overlaps on As and Se. In the study an Agilent 7500c ICP-MS with Octopole Reaction System (ORS) was used to determine As and Se in a Peach Leaf CRM. The ORS results, acquired without the use of the interference correction equations, compared more favorably with the reference values than results obtained from the non-cell ICP-MS results using interference correction equations.
In summary: ICP-MS can measure a full suite of elements in a single multi-element acquisition, offers a solution to reduce interference effects, accepts almost any sample type, and also provides isotopic information. As such the suitability for trace metal analysis of herbal medicinal products as required by the regulations is given.
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