Single-Laboratory Ruggedness Testing and Validation of a Modified QuEChERS Approach To Quantify 185 Pesticide Residues in Salmon by Liquid Chromatography– and Gas Chromatography–Tandem Mass Spectrometry

In this study, we successfully applied a previously modified version of the QuEChERS approach to quantify pesticide residues in samples of fresh salmon. Analysis was performed using a combination of liquid and gas chromatography-tandem mass spectrometry (LC-MS/MS and GC-MS/MS). The validated QuEChERS method used ethyl acetate for the extraction solvent and involved two freezing steps and a C18 dispersive solid phase extraction for removal of lipids. Of the 228 pesticides initially screened, only 185 passed the method validation criteria (103 on LC-MS/MS and 82 on GC-MS/MS). In a quantitative validation, acceptable performances were achieved with overall recoveries of 70-120% and <20% RSD for 179 analytes (n = 7) over the course of five different extractions at 2 times the limit of quantification. Over 12 months, this method was used in the analysis of 708 salmon samples collected as part of the U.S. Department of Agriculture's Pesticide Data Program. Ruggedness testing conducted throughout the entire study showed this method to be robust and suitable for long-term use.