Treatment of non-invasive biological matrix samples for screening determination of major and trace elements by inductivity coupled plasma mass spectrometry

The determination of major and trace elements in non-invasive biological matrix (i.e. human hair, breast milk, meconium, and urine) is potentially useful for assessing an individual's health status and monitoring occupational and environmental exposure [1-3]. On the other hand, owing to the lack of standardised biological matrix analysis procedures (including sample treatment methods), it is difficult to compare and interpret the results (intervals and reference values) from different studies and reach significant conclusions. Analyte loss, contamination, and/or interferences may also lead to a decrease in the analytical accuracy of the results. Incomplete decomposition of the biological matrix samples involves an appreciable amount of residual C content in the resulting sample solution. In inductively coupled plasma spectrometry (ICP) techniques, this leads to the increased signal of some elements by C charge transfer reactions, especially for elements that have similar ionisation potentials to that of C [1]. Another source of error in biological matrix analysis by ICP with mass spectrometry (ICP-MS) is the interference caused by the residual acidity in the digests, difference between the viscosity and acid concentrations of the calibration and sample solutions, and the presence of polyatomic ions in the plasma [1]. Considering these aspects, the aim of this study was to optimise and validate a fast screening analytical method for the multi-determination of elements (Al, As, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, K, La, Li, Mg, Mn, Mo, Na, Nb, Ni, P, Pb, Rb, Sb, Se, Si, Sn, Sr, Te, Ti, Tl, U, V, W, Zn, and Zr) in biological matrix samples. The samples were subjected to HNO3/H2O2 (2:1) digestion in an open vessel heated in a water bath and subsequently analysed by ICP-MS equipped with a collision-reaction interface. The digestion process, which was performed directly in polypropylene tubes, presented a significant reduction in reagent and sample amounts, treatment time, and sample handling compared to those of microwave acid digestion. Thus, the proposed method is a precise and accurate method with a high sample throughput. The in-field data can be employed as baseline information for the future elaboration of reference intervals and assessment of the nutritional status and environmental exposure of an individual.