Determination of Toxic Elements in Botanical Dietary Supplement Ingredient Reference Materials

Background The National Institute of Standards and Technology (NIST) has produced over 40 botanical dietary supplement Standard Reference Materials® (SRMs) and reference materials (RMs) with values assigned for chemical markers and/or active compounds. Although environmental accumulation or inadvertent introduction of toxic elements (arsenic, cadmium, lead, and mercury) is a potential source of exposure in botanical dietary supplement products, the majority of the dietary supplement SRMs/RMs do not have values assigned for the four major toxic elements. Objective To determine As, Cd, Pb, and Hg content in the current inventory of NIST botanical dietary supplement SRMs/RMs. Methods Fifteen SRMs/RMs suites of plant part, extract, and finished products [i.e., solid oral dosage form (SODF)] were analyzed for As, Cd, Pb, and Hg using nitric acid microwave-assisted digestion followed by quantification using inductively coupled plasma—mass spectrometry. Results Results for control samples were in good agreement with certified values indicating that the analyses of 38 individual botanical SRMs/RMs were in control. Characterization of linked plant/extract SRMs/RMs derived from the same source materials demonstrated that while extraction processes can often yield extracts with lower toxic element content for Hg or As, it is also possible for mass fraction levels to remain unchanged or even increase following extraction. Conclusion The results fill significant knowledge gaps in toxic element content ranges for SRMs/RMs where no NIST assigned values existed, in particular for Hg content and for extract and SODF matrices. With comprehensive toxic element content now available, researchers can better select appropriate dietary supplement SRMs/RMs for use as controls in the analysis of dietary supplement ingredients and products. Highlights Results for As, Cd, Pb, and Hg are reported for 38 dietary supplement SRMs/RMs including 6 suites of plant, extract, and SODF and 9 pairs of plant and extract from the same batch of plant material.