Liquid chromatography–electrospray quadrupole ion-trap mass spectrometry of nine pesticides in fruits

A liquid chromatographic method, with electrospray ionization tandem mass spectrometry (LC–ESI-MS–MS), has been developed for determining acrinathrin, carbosulfan, cyproconazole, λ-cyhalothrin, kresoxim methyl, pyrifenox, pyriproxyfen, propanil, and tebufenpyrad in fruits. The ions prominent in ESI spectra were [M + H]+ and [M + Na]+. In the mass analyzer, collision-induced dissociation fragmentation involved common pathways, for example, product ions of [M + H]+ resulted from the cleavage of the carbamic group or an oxygen bound. The utility of the method is demonstrated by the analysis of crude extracts obtained by matrix solid-phase dispersion (MSPD) using C18 as dispersant and dichloromethane-methanol as eluent, and by solid–liquid extraction (SLE) with ethyl acetate and anhydrous sodium sulfate. Mean recoveries ranged from 51.5 to 108%, with relative standard deviations <16%, were obtained for MSPD and from 59 to 101% with relative standard deviation <17% for SLE. However, for most compounds, limits of quantification are better by SLE (0.01–0.4 mg kg−1) than by MSPD (0.05–2 mg kg−1). During the validation process, the procedure was tested for matrix effects, blanks and stability of the system. Considerably matrix effects in the ESI ionization process were detected by comparing standard calibration, and matrix calibration. Because of this, detected residues were quantified from interpolation against calibration data obtained using matrix matched standards.