Simultaneous combination of MS2 workflows for pesticide multiresidue analysis with LC-QOrbitrap

Abstract

This study describes an evaluation of full-scan MS analysis combined with target and non-target MS2 acquisition along with targeted processing for pesticides in fruit and vegetables. Two databases were used comprising priority compounds (target acquisition) and less frequently detected compounds (non-target acquisition). Full-scan MS data were used for detection and quantitation, whereas MS2 data were used for identification. Target MS2 (data-dependent MS2) data were acquired for 166 pesticides with known retention times. Non-target MS2 (all-ion fragmentation MS2) data were obtained against a database containing 101 pesticides without retention times. At the level of 0.01 mg kg⁻¹, selected target pesticides were identified in 99% of the cases in tomato (the best case) and in 92% of the cases in leek (the worst case). Peak area repeatability (RSD < 20%) at 0.01 mg kg⁻¹ was satisfactory (99% of compounds in tomato and 90% in leek). In the case of non-target compounds (searched without retention times), the numbers of false-positive and false-negative results were determined. A total of seventy-two real samples were used to determine the false positives. The database search was carried out considering only the full-scan MS ion, the full-scan MS ion and one MS2 fragment, and the full-scan MS ion and two MS2 fragments. In the first case, 297 false positives were found, whereas in the second case, 7, and in the third case, 4 false positives were found. Analogical database searches were carried out for five spiked matrices to determine the false negatives. At the level of 0.01 mg kg⁻¹, three ions (one in full-scan MS and two in MS2) were found for 96% of the compounds in tomato and lettuce (the best cases) and 75% of the compounds in leek (the worst case). Two ions (one in full-scan MS and one in MS2) were detected for 100% of the pesticides in lettuce and for 95% of the pesticides in leek. These results clearly show the high analytical performance of the applied workflow, with important advantages derived by increasing the analytical scope for qualitative screening. The approach presented in this study combines the advantages of target and non-target MS2 analysis.