Simultaneous on-line preconcentration and determination of Pt, Rh and Pd in urine, serum and road dust by flow injection combined with inductively coupled plasma time-of-flight mass spectrometry

Abstract

In this work, ICP-time of flight (TOF)-MS with ultrasonic nebulisation (USN) was combined on-line with a flow injection (FI) system for the determination of Pt, Rh and Pd in biological fluids (urine and blood serum) and road dust. Simultaneous and selective preconcentration of the 3 analytes was performed by sorption of their complexes formed on-line with diethylthiourea (DET) on the inner walls of a PTFE knotted reactor (KR), in a wide range of sample acidity (0.1–0.5 M HNO₃ for Pd and Rh and 0.05–0.2 M HNO₃ for Pt). A quantitative elution was achieved using 500 µl methanol acidified with 1% HNO₃. The detection limits obtained were 0.54, 2.12 and 0.36 ng l⁻¹ for Pt, Rh and Pd, respectively, and the relative standard deviation RSD (for 50 ng l⁻¹ of Pt, Rh and 25 ng l⁻¹ of Pd, n = 6) was ≤ 3%. Using a preconcentration time of 120 s and a sample flow rate of 5 ml min⁻¹, enrichment factors of 55, 5 and 2 for Pd, Pt and Rh, respectively, were obtained in comparison with direct determination by ICP-MS without preconcentration. Special attention was paid to the study of the adverse effects of potentially interfering species present in the matrix (Cd, Cu, Pb, Sr, Fe, Y, Zn, Ni, Rb, Mn and Mo) on the preconcentration and the mass-spectrometric determination of the analytes. The accuracy of the method was demonstrated by the analysis of urine, blood serum and road dust certified reference materials. The method was applied to urine and serum samples of healthy subjects. The concentrations of Pt, Rh and Pd determined in these samples were comparable to reported values.