Influence of sample pre-treatment on the determination of trace elements in urine by quadrupole and magnetic sector field inductively coupled plasma mass spectrometry

Abstract

An investigation was carried out to explore further the analytical capabilities of quadrupole and magnetic sector field inductively coupled plasma mass spectrometry (ICP-MS) in conjunction with ultrasonic nebulization (UN) for the reliable determination in human urine of nine potentially toxic and/or environmentally relevant trace elements, namely Cd, Co, Cr, Ni, Pb, Rb, Sb, Se and V. For the quantification of Cr, Ni and V magnetic sector field ICP-MS was used in the medium resolution mode (m/Δm=3000) to separate the signal of the analyte from severe polyatomic interferences caused by high concentrations of bulk elements (C, Ca and Cl). The detection power afforded by quadrupole ICP-MS, on the other hand, was adequate for the reliable determination of Cd, Co, Pb, Rb, Sb and Se. Three different sample pre-treatment steps, namely dilution of urine with high-purity water, UV irradiation and microwave digestion with concentrated HNO₃ and H₂O₂, were investigated in detail to clarify two key issues, i.e., first, the performance, accuracy and reproducibility of the two ICP-MS systems under different matrix loads of the plasma and, second, the actual concentrations of trace elements in the urine sediment.