Simultaneous multi-elemental speciation analysis of organometallic compounds by solid-phase microextraction and multicapillary gas chromatography hyphenated to inductively coupled plasma-time-of-flight-mass spectrometry

Abstract

A simple, rapid and accurate method on the basis of solid phase microextraction (SPME) in combination with multicapillary gas chromatography (MCGC) hyphenated to inductively coupled plasma-time-of-flight mass spectrometry (ICP-TOFMS) was developed for simultaneous speciation analysis of 10 organometallic compounds of mercury (including inorganic mercury), tin and lead. Headspace SPME was used for extraction/preconcentration of the species from the sample after derivatization with sodium tetraethylborate and subsequent volatilization. Seven SPME fibers were compared in terms of extraction efficiency. A 65 µm polydimethylsiloxane/divinylbenzene fiber offered the best overall extraction efficiency. Using MCGC separation, a total chromatographic run time below 200 s was obtained. With ICP-TOFMS detection peak widths at half height (FWHM) down to 0.3 s were measured without spectral skew thanks to the simultaneous character of the mass spectrometer. Detection limits well below pg g−1 levels were obtained for trimethyllead (TML), dimethyllead (DML), trimethyltin (TMT), dimethyltin (DMT), monomethyltin (MMT), monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT). Somewhat higher detection limits were obtained for methylmercury (MeHg, 1.3 pg g−1) and inorganic mercury (Hg2+, 2.0 pg g−1). For extraction/preconcentration of MeHg and Hg2+ the 75 µm carboxen/polydimethylsiloxane (CAR/PDMS) fiber is a better choice. The analytical precision (RSD, %) for 10 successive injections of a standard mixture containing 100 pg of each species was generally below 5%. Propylmercury (PrHg) was used as the internal standard for MeHg and Hg2+ as well as for lead species determination. The method was validated by the analysis of biological and road dust certified reference materials (CRMs).