Instrumental comparison for the determination of cadmium and lead in calcium supplements and other calcium-rich matrices

Three brands of Ca supplement, a laboratory-reagent grade CaCO3 and a certified reference material (International Atomic Energy Agency H-5 Animal Bone) were analysed for Cd and Pb by four different analytical techniques, viz., anodic stripping voltammetry, inductively coupled plasma mass spectrometry, flame atomic absorption spectrometry and electrothermal atomic absorption spectrometry. The Pb levels measured by the four techniques in the bone powder were within the certified Pb level in this certified reference material. Similarly, no significant differences [p <0.05; analysis of variance (ANOVA)] were observed in samples with Pb concentrations greater than 1 µg g–1. However, the Pb levels in the laboratory-reagent grade CaCO3 obtained by flame atomic absorption spectrometry (0.79 µg g–1) averaged about three times higher than those measured by the other three techniques (i.e., 0.25 µg g–1). Although no significant differences (p <0.05; ANOVA) in Cd levels were observed within any of the samples (intra-sample variability), the Cd concentration measured in the different Ca supplements (inter-sample variability) varied by three orders of magnitude (ranging from 0.07 to 3.59 µg g–1).