A sensitive technique for speciation and quantification of Cr(III), Cr(VI), and total chromium has been developed using high-pressure liquid chromatography (HPLC) combined with direct injection nebulization (DIN) and inductively coupled plasma mass spectrometry (ICP-MS). A characterization and optimization of a microcolumn specifically designed for chromium speciation has been conducted. The direct injection nebulizer (DIN) was optimized to produce the best possible sensitivity for the system. Parameters affecting the column component of the system such as sample pH, eluent strength, sample size, flow, and pressure characteristics were studied in addition to optimal DIN-ICP-MS parameters. The detec-ACKNOWLEDGMENT Many thanks to Lian Shan Liu, George Wood, and other staff of the Laboratory Services Branch of Ministry of the Environment and Energy for their invaluable help in making this publication possible.
Three brands of Ca supplement, a laboratory-reagent grade CaCO3 and a certified reference material (International Atomic Energy Agency H-5 Animal Bone) wee 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 less than 0.05; analysis of variance (ANOVA)] were observed in samples with Pb concentrations greater than 1 microgram g-1. However, the Pb levels in the laboratory-reagent grade CaCO3 obtained by flame atomic absorption spectrometry (0.79 micrograms g-1) averaged about three times higher than those measured by the other three techniques (i.e., 0.25 micrograms g-1). Although no significant differences (p less than 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 micrograms g-1).
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