Author(s): Jack Cochran1, Julie Kowalski1, Jason Thomas1, Michelle Misselwitz1, Rebecca Wittrig2*, Andre Schreiber3
1Restek Corporation, 110 Benner Circle, Bellefonte, Pennsylvania 16823, USA
2AB SCIEX, 353 Hatch Drive, Foster City, California 94404, USA
3AB SCIEX Research and Development, 71 Four Valley Drive, Concord, Ontario, Canada L4K 4V8
*Current address: Restek Corporation, 110 Benner Circle, Bellefonte, Pennsylvania 16823, USA
Published By: Restek Corporation
Year of Publication: 2012
Abstract: Food commodities were fortified with pesticides and processed using the QuEChERS sample preparation technique. Samples were analyzed by both GCxGC-TOFMS and LC-MS/MS. The foods chosen varied in water, fat, and pigment content, so the ruggedness of QuEChERS as well as the performance of GCxGC-TOFMS and LC-MS/MS could be assessed. Commodities tested were red bell pepper, cucumber, black seedless grape, spinach, lemon, raisin, and hazelnut. Recovery values were determined by matrix-matched standards for the GC method and by solvent standards for the LC method. Evaluation of GCxGC-TOFMS and LC-MS/MS, along with the QuEChERS approach itself, was made by comparison of recovery values and incurred pesticide concentrations.
Good recoveries were obtained for most pesticides in most commodities as determined by GCxGC-TOFMS and LC-MS/MS. Sometimes GCxGC-TOFMS did not have the selectivity necessary for determining certain pesticides in the most complex samples. In this regard, dispersive SPE (dSPE) cleanup was ineffective at removing significant matrix interferences in lemon, raisin, and hazelnut extracts for some target pesticides. Corrupted LC-MS/MS quantification for some pesticides was observed, especially in lemon and hazelnut extracts, and likely resulted from ion suppression or was due to quantification by solvent-only standards. Incurred pesticide quantifications were comparable for GCxGC-TOFMS and LC-MS/MS. GCxGC-TOFMS was able to identify non-target pesticides.