The utility of ultra‐performance liquid chromatography/electrospray ionisation time‐of‐flight mass spectrometry for multi‐residue determination of pesticides in strawberry

Abstract

The utility of ultra-performance liquid chromatography/orthogonal-acceleration time-of flight mass spectrometry (UPLC/TOFMS) for the rapid qualitative and quantitative analysis of 100 pesticides targeted in strawberry was assessed by comparing results with those obtained using a validated in-house UPLC tandem mass spectrometry (MS/MS) multi-residue method. Crude extracts from retail strawberry samples received as part of the 2007 annual UK pesticide residues in food surveillance programme were screened for the presence of pesticide residues using UPLC/TOFMS. Accurate mass measurement of positive and negative ions allowed their extraction following 'full mass range data acquisition' with negligible interference from background or co-eluting species observed during UPLC gradient separation (in a cycle time of just 6.5 min per run). Extracted ion data was used to construct calibration curves and to detect and identify any incurred residues (i.e. pesticides incorporated in or on the test material following application during cultivation, harvest and storage). Calibration using matrix-matched standards was performed over a narrow concentration range of 0.005-0.04 mg kg(-1) with determination coefficients (r2) > or =0.99 for all analytes with the exception of malathion/fenarimol/fludioxanil (r2 = 0.98), quassia/pymetrazine (r2 = 0.97) and fenthion sulfone (r2 = 0.95). Residues found in selected samples ranged from 0.025-0.28 mg kg(-1) and were in excellent agreement with results obtained using UPLC/MS/MS. Mass measurement accuracies of < or =5 ppm were achieved consistently throughout the separation, mass range and concentration range of interest thus providing the opportunity to obtain discrete elemental compositions of target ions.

Current mass spectrometry strategies for the analysis of pesticides and their metabolites in food and water matrices

“…A comparison between LC-MS/MS and UPLC-MS/MS chromatograms of apple crude extract spiked with 17 pesticides is illustrated in Figure 1, which clearly demonstrates the gains in analysis time and resolution using UPLC. Applications of UPLC hyphenated with TOF-MS (Taylor et al, 2008) and QqTOF-MS (Picó et al, 2007bWang & Leung, 2009) for pesticide residues analysis have been also reported.…”

“…In another direct comparison for the determination of 16 pesticides and transformation products in baby foods, UPLC yielded enhanced S/N ratios, narrower peaks and decreased analysis times over HPLC (Leandro et al, 2006). UPLC-QqQ-MS in multi-residue analysis of pesticides aims to increase the number of monitored compounds, reduce the time of the LC separation step and improve the performance characteristics of the determination step (Lambropoulou & Albanis, 2007;Leandro et al, 2007b;Pozo et al, 2007;Gervais et al, 2008;Kovalczuk et al, 2008;Marín et al, 2009;Mol et al, 2008;Taylor et al, 2008;Wang & Leung, 2009). More than 50 pesticides have been determined in alcoholic beverages by UPLC-QqQ-MS in a run time of 11 min acquiring two transitions per analyte (Plaza Bolãnos et al, 2008) while 90 pesticides have been determined in fruit juices by UPLC-QqQ-MS in MRM mode, in the same run time of 11 min (Romero-González, .…”

“…The SE treatment is occasionally performed with ultrasonication to increase the extraction yield and increase the speed of the procedure (Pan, Xia, & Liang, 2008). Extraction conditions, in particular pH, must usually be adjusted to facilitate analyte extraction using formic acid Mol et al, 2008) acetic acid (Poulsen et al, 2007), buffers (Mol et al, 2007;Nanita, Pentz, & Bramble, 2009;Esparza, Moyano, & Galceran, 2009), monobasic sodium carbonate (Pihlström et al, 2007;Taylor et al, 2008), and sodium hydroxide (Dreassi et al, 2007). In a recent study, acetonitrile, methanol, and acetone, all buffered with formic acid, were compared for a generic SE method for the LC-MS determination of 136 multi-class pesticides in different food matrices; overall, acetonitrile was deemed the best compromise (Mol et al, 2008).…”

“…The application of MS platforms for the analysis of pesticides include: (1) the determination of pesticide residues in food to ensure safety of the food supply (Botitsi, Economou, & Tsipi, 2007;Leandro et al, 2007b;Pizzutti et al, 2007;Mol et al, 2008;Taylor et al, 2008;Garrido Frenich et al, 2008a); (2) the investigation of the contamination of water resources from pesticides and their relevant metabolites Perreau et al, 2007;Potter, Mohamed, & Ali, 2007;Carvalho et al, 2008;Gervais et al, 2008;Greulich & Alder, 2008;Marín et al, 2009); (3) the elucidation of the structure of unknown degradation/transformation products or metabolites that sometimes can be more toxic than the parent pesticide (García-Reyes, Richardson, 2008). Several reviews published in a 2006 special issue of Mass Spectrometry Reviews have focused on the use of MS-based methods for analyzing pesticides and their degradation products in food and water matrices (Alder et al, 2006;Kuster, López de Alda, & Barceló, 2006;Lacorte & Fernández Alba, 2006;Niessen, Manini, & Andreoli, 2006;Picó et al, 2006).…”

Liquid Chromatography-Mass Spectrometry in the Analysis of Pesticide Residues in Food

“…Its separation efficiency, up to 40,000, considerably exceeds the separation efficiency of the quadrupole analyzer. In the analysis of pesticide residues in food, the time-of-flight analyzer is mainly used to confirm the presence of the compounds of interest in matrices such as fruit and vegetables (Mezcua et al 2009;Taylor et al 2008), honey and meat (Mol et al 2008), fruit beverages GarciaReyes et al 2008), and wine (Perez-Ortega et al 2012).…”