Flow injection analysis with inductively coupled plasma time-of-flight mass spectrometry for the simultaneous determination of elements forming hydrides and its application to urine

The use of an inductively coupled plasma mass spectrometer (ICP-MS) with a time-of-flight (TOF) analyser is illustrated for the simultaneous determination of seven elements forming hydrides (As, Bi, Ge, Hg, Sb, Se and Sn) using flow injection (FI) as the sample introduction system. The chemical conditions for an adequate simultaneous volatile species generation as well as the plasma parameters for simultaneous determination were evaluated. The compromise hydride generation conditions were: 1% NaBH4 and 0.7 M HNO3 final concentration, while an Ar carrier gas flow rate of 1.1 l min−1 provided optimum results for the transport of the volatile species to the ICP-MS. Analytical figures of merit were evaluated under these compromise conditions and compared with those obtained by continuous nebulisation of the same elements in the ICP-MS(TOF). Detection limits in the low pg ml−1 region, linearity over more than five orders of magnitude and repeatability of 2–5% were achieved with the proposed methodology. Application of such a strategy was demonstrated by the simultaneous multi-elemental determination of As, Bi, Ge, Hg, Sb, Se and Sn in spiked urine samples with recoveries better than 80%. For Se, accurate results were only obtained by avoiding volatile species generation, demonstrating the presence of selenium species other than Se(IV) in human urine. The accuracy of the method was also checked by analysing a certified urine sample (NIST SRM 2670) by FI-ICP-MS(TOF) with satisfactory results.