. . and soil, respectively. The cumulative health effects of these Cd and Co were the most in the gastric juice at all the tested concentrations. The accumulation of Cd and Co in hair was 6.3 and 5.9%, respectively. The average Cd and Co concentrations in human blood was 0.13 and 0.17 μg/L. This study indicated that consumption of this metal containing foods can pose risks to health.
Recent progress in mass spectrometry has given rise to an increased ability to conduct rigorous chemical speciation studies on anthropogenic contaminants, even when found in minute quantities. Since the late 1970's, it has been the principal modality for analysis of metal toxicity in an attempt to establish standards to protect the public. The work of Smith et al. (1999) has used matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF) to speciate chromium in the environment. The approach uses the recent observation that protons and metal species can be ionized under the same conditions, and then differentially ionized by the laser. This method, along with isotope labeling, represents a promising new tool for speciation of trace metals in complex mixtures. More recently, this approach has been applied to chromium and some other trace metals in complex environmental samples, including marine sediments.
To provide more information on the speciation of chromium in the environment, a laboratory study was conducted to examine the effects of pH and aqua regia on the speciation of chromium at very low concentrations in natural and synthetic solutions. Experiments were also conducted to determine if the mechanism of chromium speciation changes with pH.
Experiments were performed to determine the effect of addition of equimolar amounts of sodium chloride to ternary and quaternary compositions at various pH values on the speciation of Cr(VI) and Cr(III). Samples were digested with aqua regia and analyzed by an inductively coupled plasma mass spectrometer (ICP-MS). In addition, Cr(III) and Cr(VI) in solution were extracted into ethyl acetate and analyzed by MALDI-TOF mass spectrometry. In all cases, the following species were identified: chromium(III), chromium(VI) and chromium(III)-chloride species, where octahedral [Cr(VI)Cl6]3- was identified at
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