GC-MS/MS TSQ 9000 (Thermo Scientific)

The triple quadrupole TSQ 9000 is coupled with Trace 1300 gas chromatograph (Thermo Scientific). The mass spectrometer can be operated in EI and positive or negative CI modes of ionization. Data can be acquired in full scan, SIM, product ion scan, and MRM modes. Either helium or hydrogen can be used as carrier gas for the GC separations. The GC-MS/MS system is equipped with RSH (CTC)  autosampler, which has liquid, static headspace, and SPME injection options. The fiber cleaning station is available for reducing carryover contamination of SPME analysis. Two gases namely, methane and isobutane, are available for CI studies.

The instrument can be used for targeted quantitative analysis, structure elucidation, and screening analysis of unknowns that do not require high sensitivity. The combination of EI, CI, and MS/MS is very useful for the analysis of unknowns. Negative CI is of particular interest in analyzing high electron affinity compounds (containing electronegative groups like halogens, nitro, etc.).

Available software: Xcalibur, TraceFinder.

Chemical ionization is a rarely used technique despite obvious advantages. Here are negative CI (methane) GC-MS chromatograms of polychlorinated biphenyls standard mix. The EIC chromatogram of chloride (m/z 35, 37, blue) fits with the above TIC chromatogram (total ion count, black) of detected PCBs as expected. This standard mix is not supposed to include bromo-organic compounds yet there were detected two in the EIC chromatograms of bromide (m/z 79, 81, red). Bromo-organic compounds present at trace levels in commercially available PCB mix could be detected neither using EI nor positive CI ionization methods.

Negative CI (methane) mass spectrum of bromo-organic compound detected in PCB standards mix. In the negative CI, electronegative halogen captures a cold electron and as a result, the Hal ̶ C bond may be broken giving rise to a  halide anion, quite often the only detectable ionization product.

The GC-MS/MS TSQ 9000 applications

• Analysis of mono- and disaccharides

• Analysis of geosmin and methylisoborneol in pool water

• Analysis of polycyclic aromatic hydrocarbons

• Analysis of chlorinated pesticides