Comparison of targeted and nontargeted approaches for the identification of pesticides and environmental contaminants in foods by gas chromatography – high resolution mass spectrometry

Description:
For gas chromatographic (GC) analysis of chemical contaminants in foods and the environment, tandem mass spectrometry (MS/MS) of targeted analytes has become the gold standard approach due to its exceptional selectivity and sensitivity. However, nontargeted chemicals of concern are not monitored in GC-MS/MS, which leads to potential false negatives by omission. Nontargeted screening with high-resolution mass spectrometry (HRMS) is becoming more common, but chemical identification without known standards is a questionable practice. GC-HRMS can be used for targeted analysis as in GC-MS/MS, but with the added benefit to allow retrospective analysis of additional analytes after they’ve been added to the target list. The aim of this work was to compare targeted vs. nontargeted analysis of spiked pesticides and environmental contaminants in different foods by GC-HRMS (orbital ion trap) using different software programs. QuEChERSER sample preparation was used to yield barley, eggs, and hemp final extracts with 10 replicates each containing 250 analytes at 4 concentration levels ranging from 1-100 ng/g plus 20 blanks. In targeted analysis, mass accuracy of 3 ion fragments (<5 ppm) included in a user-customized compound database of known retention times was used for analyte identification, yielding false(+) and false(-) rates of 1% and 14%, respectively, with average LOQ of 2.9 ng/g. Compound Discoverer software was used for nontargeted analysis and qualitative identification performance will be compared and presented.

Speaker: Nicolas Michlig - USDA