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The analysis of chlorinated pesticides has traditionally been performed
using an Electron Capture Detector (ECD) with confirmational analysis by GC/MS
using Full Scan (FS). FS GC/MS has sensitivity limitations that prohibit
it from confirming ECD hits at very low levels. To improve sensitivity,
Selective Ion Monitoring (SIM) has been used; however, SIM may
be susceptible to ion interferences from matrix.
An alternative approach is tandem mass spectrometry
(MS/MS), where a target compound ion is isolated from matrix and then fragmented
to generate very unique spectra. A list of chlorinated pesticides was studied in
a vegetable matrix by sequential Full Scan (FS) and SIM analysis on the Thermo
Scientific DSQ series single quadrupole GC/MS system, and then by FS and MS/MS analysis on the PolarisQ Ion Trap GC/MSn. The linearity and precision were examined using internal standards to track any degradation of response.
Both methods can be successful for analyzing
pesticides in vegetables, although MS/MS appears less prone to false positives and provides reliable and accurate results. |
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