Source apportionment of bioaccessible lead in soil reference materials using the continuous on-line leaching method and inductively coupled plasma mass spectrometry

Bioaccessibility (the amount of a contaminant extracted by the gastrointestinal fluids during digestion) is often incorporated in the assessment of contaminated soils and foods. Current methods, including those published by the United States Environmental Protection Agency (US EPA) and United States Pharmacopoeia (USP), use a batch method of analysis which requires hours of extraction prior to instrumental analysis with inductively coupled plasma mass spectrometry (ICPMS). The continuous on-line leaching method (COLM) uses a more direct method of analysis as extracts are sent directly to the ICPMS instrument, which can reduce extraction time and give real-time elution kinetics. For this study, four reference soils (NIST 2710, NIST 2710a, NIST 2711a, and BGS 102) that are typically used with bioaccessibility methods were extracted using the COLM and US EPA and USP gastrointestinal fluids. With the transient time-resolved data from the COLM, differential elution indicating multiple Pb sources was observed in NIST 2710a, NIST 2711a, and BGS 102. Two methods for calculating the Pb isotope ratios to identify these sources included a point-by-point ratio average method and a more precise regression slope method. There was no statistically significant difference between the ratios obtained by these methods of calculation. Furthermore, NIST 2710a and NIST 2711a did not have any statistically significant difference between the Pb isotope ratios of two observed sources. BGS 102 had a significantly different secondary source of Pb, which was identified to be from Pb historically added to gasoline. Investigation into the regions these soil reference materials were sourced from supported this finding as BGS 102 comes from a more densely populated, industrialized area where soil contamination with Pb from gasoline is likely to be more prevalent. This type of bioaccessibility investigation is only possible with the COLM as it gives real time elution information. Incorporation of the COLM into future bioaccessibility studies (and inclusion of other elements for isotopic analysis, like Sr) will lead to more thorough and comprehensive bioaccessibility studies in the future.

Toxic metal levels in cocoa powder and chocolate by ICP-MS method after microwave-assisted digestion

The Commission Regulation (EC) Regulation N. 488/2014, established the concentration limits for cadmium in specific products based on cocoa and chocolate products as from January 2019. Based on this information there is a need to determine ultratrace levels of elements that might be presents in cocoa and chocolate products. In this work, the concentrations of Arsenic, Antimony, Cadmium, Chromium, Lead, Selenium and Vanadium were evaluated in cocoa powder and chocolate by the validation of an ICP-MS method. Good selectivity/specificity, recovery, repeatability and within-laboratory reproducibility, LOD, LOQ, range of linearity, standard measurement uncertainty parameters for method validation were achieved, in accordance with Commission Regulation. The cocoa powder revealed the maximum metal concentrations of 0.303 ± 0.035 mg/kg for cadmium, 1.228 ± 0.146 mg/kg for lead and 0.094 ± 0.013 mg/kg for arsenic. A significant difference was found between cocoa powder and chocolate samples (p < .05).