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Evaluation of MS2 workflows in LC-Q-Orbitrap for pesticide multi-residue methods in fruits and vegetables

Rajski, Łukasz, del Mar Gómez Ramos, María, Fernández-Alba, Amadeo R.
Analytical and bioanalytical chemistry 2017 v.409 no.23 pp. 5389-5400
acetonitrile, chromatography, false negative results, food contamination, fruits, multiresidue analysis, pesticide residues, pesticides, screening, vegetables
LC-Q-Orbitrap efficiency was evaluated for pesticide multi-residue analysis by using three workflows involving simultaneous MS and MS² analysis. They were as follows: data-dependent MS² (dd-MS²), all-ion fragmentation (AIF) and variable data-independent analysis (vDIA). These MS² workflows were tested for the main method validation parameters such as detection and identification capabilities, repeatability, linear range and quantitation. QuEChER acetonitrile extracts (blanks and spiked with 166 pesticides) of 11 different fruits and vegetables were used for this evaluation. Blank extracts were analysed to evaluate isobaric compounds and potential false identification. Spiked extracts (at 0.01 and 0.1 mg kg⁻¹) were analysed to evaluate the false negatives potentially produced (considering a retention mass window of 0.2 min). At 0.01 mg kg⁻¹, dd-MS² had the highest identification rate (96–100%, depending on the matrix). In vDIA, it was 86–100% and in AIF 81–100%. But these two last workflows offered more possibilities for applying screening analysis. It was observed that application of the ion ratio criterion established in the SANTE Guidelines for identification can generate some artificial false negative results. It could be overcome by considering a mass error threshold (i.e. 5 ppm) as a selected criterion. Detection and quantitation were carried out in full-scan MS. MS² data were used for identification. Dd-MS² provided the highest number of points per chromatographic peak, and by that peak area, repeatability was the best (typically <10%). AIF and vDIA were characterised by longer cycle times; thus, the obtained peak area repeatability was slightly worse, but acceptable (<20%). All workflows showed very good linearity in the range 0.01–0.5 mg kg⁻¹. The three MS² workflows were applied to real samples with good results. Graphical abstract LC-Q-Orbitrap was used for pesticide residues analysis in fruit and vegetables. Three approaches to MS² identificaton were evaluated