Speciation of organometals using a synchronizing GC-EIMS and GC-ICPMS system for simultaneous detection
In analytical chemistry, improvement in instrument performances is always important for achieving better analytical results and obtaining more information on the target analytes. Gas chromatography-inductively coupled plasma mass spectrometry (GC-ICPMS), which combines powerful separation ability and high sensitivity, has found broad applications in sensitive speciation of organometals such as methylmercury (MeHg), butyltin (BuSn), and seleniomethionine (SeMet). Unfortunately, GC-ICPMS is unable to provide molecular information of the analytes such as molecular fragmentations or isotopic patterns, which are very important for identifying target analytes. A method is reported for the simultaneous determination of organometals including MeHg, dibutyltin (DBT), tributyltin (TBT) and SeMet using a unique interface with gas chromatography-electron ionization mass spectrometry (GC-EIMS) and GC-ICPMS systems synchronously. The method was validated with measurements of MeHg, DBT, TBT and SeMet in the certified reference materials (CRMs) including dogfish liver (DOLT-4), marine sediments (PACS-2) and selenium-enriched yeast (SELM-1). Compared with EIMS, ICPMS achieved a remarkable gain in sensitivity for MeHg, DBT and SeMet (19-, 130- and 2850-fold S/N gain, respectively). The concentrations of MeHg (1.335 ± 0.033 μg g−1), DBT (1.171 ± 0.005 μg g−1) and TBT (0.834 ± 0.003 μg g−1) obtained with isotope dilution are in agreement with the certified values of the corresponding CRMs. With the proposed method, the ICPMS system can provide higher precision and sensitivity, and the EIMS system can provide information on the molecular structure, which is essential for identification of target analytes.