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Which GC instrument should I use for the analysis of pesticides in herbal tea? GC-MS/MS or GCxGC-TOFMS?

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  • Michelle Misselwitz
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You may remember a while ago I posted a blog about the analysis of herbal tea using QuEChERS and GCxGC-TOFMS.   The LECO Pegasus GCxGC-TOFMS is a great instrument for analyzing complex samples because of the comprehensive chromatographic separation achieved (two columns with different selectivities).  The GCxGC-TOFMS also excels at non-target screening of compounds.  Lucky for us, we also have a Thermo TSQ 8000 GC-MS/MS in our lab to use.  The GC-MS/MS is also a great instrument for analyzing complex samples, like herbal tea, because of the selectivity afforded by the Selected Reaction Monitoring (SRM) transitions.  While the GC-MS/MS cannot do non-target screening like the TOFMS can, it is significantly more sensitive for targeted analysis.   My colleague Julie Kowalski and I set out to do a head to head comparison of the two instruments for the analysis of pesticides in herbal tea.  Check out the data and analysis conditions in my presentation that I gave at the recent EPA Region 6 Quality Assurance Conference in Dallas, TX.

Overall the instruments performed similarly, with only a few notable differences.  One of the major differences was that we could accurately quantify at the 10 ppb fortification level (5 pg on-column) on the GC-MS/MS where we could not get that sensitivity on the GCxGC-TOFMS system.

So which GC instrument should I choose for the TARGETED analysis of pesticides in herbal tea - the GC-MS/MS.  However, I couldn't do this with the GC-MS/MS though.  So, in the end I am happy to have both instruments in the lab! Please let me know if you have any questions or want more info on this analysis.