Optimization of an acidic digestion method for the determination of total Pb concentration and its isotope ratios in human blood using ICP-QMS

ABSTRACT

Adverse effects of lead (Pb) on human health are observed even at levels below 5 μg/dL, affecting principally the children population and suggesting that there is not a safe exposure level. The determination of Pb isotopic ratios (LIRs) in biological and environmental samples, is an appropriate tool to track and control the exposure sources, because LIRs constitutes the pollutant's isotopic signature and hence can be used to identify sources of Pb emission. This study proposes the optimization of a method in order to significantly reduce the biological samples' matrix interferences, and improves precision and accuracy in the measurements of LIRs. Four total blood digestion methods were evaluated and the results were subjected to statistical methods (ANOVA) determining the combination of HNO₃:H₂O₂ (2:1 v v⁻¹)/g from a sample on a hot plate as the best of them. For the method's validation, detection and quantification limits, linearity range, intermediate precision and recovery were evaluated. The total Pb (Pb_T) and LIRs were performed by ICP-QMS, defining the optimal value of detector dead time (DT), and correcting mass bias and instrumental drift for this matrix. LIRs based on ²⁰⁶Pb, ²⁰⁷Pb and ²⁰⁸Pb were determined at high precision (%RSD 0.03–0.49%), than those involving ²⁰⁴Pb (%RSD > 0.8). The optimized methodology can be used to identify pollution sources in blood and environmental samples using LIRs (²⁰⁶Pb/²⁰⁷Pb, ²⁰⁷Pb/²⁰⁸Pb, ²⁰⁸Pb/²⁰⁶Pb, etc.) in a trustworthy and simple way, with accurate results.

KEYWORDS:

• Blood digestion
• blood lead
• ICP-QMS
• lead isotopic ratios

Acknowledgments

The authors acknowledge the support provided by the Geochemistry Laboratory of the Geological Institute's team, and the Center for Applied Research in Environment and Health, CIACYT-Medicine, both from the Autonomous University of San Luis Potosi. In addition, the authors appreciate the experimental support of Carrizales Yaez L. and Garcia-Arreola M.A., as well as the reviewers' comments, which have contributed to improve this paper.