Response surface optimization for determination of pesticide residues in grapes using MSPD and GC-MS: assessment of global uncertainty |
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Authors: | L Lagunas-Allué J Sanz-Asensio M T Martínez-Soria |
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Institution: | 1. Departamento de Química, Universidad de La Rioja, Madre de Dios, 51, 26006, La Rioja, Spain
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Abstract: | In this work, a simple and low-cost method based on matrix solid-phase dispersion (MSPD) and gas chromatography to determine
eight multi-class pesticides such as vinclozolin, dichlofluanid, penconazol, captan, quinoxyfen, fluquinconazol, boscalid,
and pyraclostrobin in grapes is described. Fungicide residues were identified and quantified using gas chromatography–mass
spectrometry in selected ion monitoring mode (GC-MS, SIM). The experimental variables that affect the MSPD method, such as
the amount of solid phase, solvent nature and elution volume were optimized using an experimental design. The best results
were obtained using 0.5 g of grapes, 1.0 g of silica as clean-up sorbent, 1.50 g of C18 as bonded phase and 10 mL of dichloromethane/ethyl acetate (1:1, v/v) as eluting solvent. Significant matrix effects observed for most of the pesticides tested were eliminated using matrix-matched
standards. The pesticide recoveries in grapes samples were better than 80% except for captan. Intra-laboratory precision in
terms of Horwitz ratio of the pesticides evaluated was below 0.5, suggesting ruggedness of the method. The quantification
limits of the pesticides were in the range of 3.4–8.7 μg kg−1, which were lower than the maximum residue limits (MRLs) of the pesticides in grapes samples established by the European
legislation. Decision limits (CCα) and detection capability (CCβ) have been calculated. The expanded uncertainties at two levels of concentration were <20% for all analytes. |
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