Determination of Heavy Metals in DietarySupplements by Inductively Coupled Plasma-Mass Spectrometry

The heavy metal content in botanicals and dietary supplements are commonly studied from the viewpoint of toxicity and bioavailability. Heavy metals such as Pb, Cd, Hg and As may be introduced in a variety of ways, including contamination during cultivation, processing and storage¹. Plant roots and leaves may absorb heavy metals from the atmosphere, water and soil. The distribution of heavy metals varies greatly within different parts of plants [1]. A simple, sensitive, and rapid method was developed for the determination of heavy metals (Hg, Pb, Cd, As, Cr, Tl, Fe, Cu, Mn, Ag, Ni, Al and Be) in plant samples and dietary supplements of Ginkgo biloba, Hypericum perforatum, Schisandra chinensis, Hoodia gordonii, Ephedra sinica, Polygonum multiflorum and Eurycoma longifolia by using closed-vessel microwave digestion with inductively coupled plasma-mass spectrometry. The results obtained by the different modes of calibration were in good agreement for plant samples and dietary products. The method was found to have good accuracy for the analysis of samples. Method precision based on analyses of different types of samples on different days for different levels was between 1.0 and 3.0% (relative std. deviation, n = 5). Significant matrix interference was not observed for the samples analyzed. The content (µg/g) of heavy metals in 7 different plant samples and 18 dietary supplements are shown in Figure 1 and represent the mean of two replicate analysis. Acknowledgements: This research is funded in part by “Science Based Authentication of Dietary Supplements” funded by the Food and Drug Administration grant number 2 U01 FD 002071-07. References: [1] Priyadarshini Raman et al., (2004), Journal of Agricultural and Food Chemistry 52: 7822–7827.

Fig. 1 Content (µg/g) of elements in different plant samples and dietary supplements