Multicapillary gas chromatography coupled to inductively coupled plasma–time-of-flight mass spectrometry for rapid mercury speciation analysis

Abstract

A simple, rapid and accurate method on the basis of multicapillary gas chromatography (MCGC) combined with inductively coupled plasma–time-of-flight mass spectrometry (ICP–TOFMS) was developed for speciation analysis of methylmercury (MeHg +) and inorganic mercury (Hg 2+). The potential of the ICP–TOFMS for transient multi-isotope detection of very short signals (peak width of 0.4 s at half peak height) was evaluated. Two injection systems (purge-and-trap (PTI) and split (SI) injections) were compared in terms of species separation resolution and transient signal profile. Using purge-and-trap injection, after in situ derivatization of the ionic mercury species with sodium tetraethylborate, a baseline separation of MeHg + and Hg 2+ was achieved within a chromatographic run of <35 s. To correct for matrix-induced ion signal variation and instrumental drift, propylmercury (PrHg +) was used as internal standard. Detection limits of 16 and 257 fg g −1 for MeHg + (as Hg) and Hg 2+, respectively, were achieved. The analytical precision (R.S.D. (%)) for 10 successive injections of a standard mixture containing 10 pg MeHg + (as Hg) and Hg 2+ was 1.2% for MeHg + and 4.1% for Hg 2+. The method was validated by analysis of two biological certified reference materials (CRM): a dogfish muscle (DORM-2) and a freeze-dried tuna fish (CRM 464).