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The coupling of reversed-phase high-performance liquid chromatography (RP-HPLC) with inductively coupled plasma mass spectrometry (ICP-MS) using post-column isotope dilution analysis (ID) was applied to the study of cadmium binding to standard rabbit liver metallothionein isoform 1 (MT-1). The analytical performance of three different ICP mass spectrometers, time of flight (TOF), double focussing (DF) and quadrupole (Q), was compared according to their performance for cadmium detection during chromatographic separation. Chromatographic conditions were optimised on a Vydac C8 VHP 259 RP column using a water–methanol gradient. Seven different sub-isoforms were distinguished by using this column coupled to a UV–Vis spectrophotometer, which greatly improved the resolution power exhibited by conventional anion-exchange chromatography. The ICP-DF-MS instrument was seriously affected by the methanol gradient and, thereafter, showed the worst performance in all cases. In contrast, the ICP-TOF-MS was able to resist up to 50% methanol with no serious changes in sensitivity or plasma stability. This instrument exhibited the lowest detection limits. The ICP-Q-MS provided results in between the other two instruments. In all cases, the use of post-column isotope dilution analysis was able to correct for matrix effects and signal drift, allowing for accurate determination of total MT concentration and the actual distribution of Cd-binding sub-isoforms.

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.