Negative chemical ionization gas chromatography coupled to hybrid quadrupole time-of-flight mass spectrometry and automated accurate mass data processing for determination of pesticides in fruit and vegetables.

Abstract

Gas chromatography coupled to high resolution hybrid quadrupole time-of-flight mass spectrometry (GC-QTOF MS), operating in negative chemical ionization (NCI) mode and combining full scan with MSMS experiments using accurate mass analysis, has been explored for the automated determination of pesticide residues in fruit and vegetables. Seventy compounds were included in this approach where 50% of them are not approved by the EU legislation. A global 76% of the analytes could be identified at 1μgkg(-1). Recovery studies were developed at three concentration levels (1, 5, and 10μgkg(-1)). Seventy-seven percent of the detected pesticides at the lowest level yielded recoveries within the 70%-120% range, whereas 94% could be quantified at 5μgkg(-1), and the 100% were determined at 10μgkg(-1). Good repeatability, expressed as relative standard deviation (RSD <20%), was obtained for all compounds. The main drawback of the method was the limited dynamic range that was observed for some analytes that can be overcome either diluting the sample or lowering the injection volume. A home-made database was developed and applied to an automatic accurate mass data processing. Measured mass accuracies of the generated ions were mainly less than 5ppm for at least one diagnostic ion. When only one ion was obtained in the single-stage NCI-MS, a representative product ion from MSMS experiments was used as identification criterion. A total of 30 real samples were analyzed and 67% of the samples were positive for 12 different pesticides in the range 1.0-1321.3μgkg(-1).