Fast GC-MS Pesticide Multiresidue Analysis of Apples

A fast gas chromatographic-mass spectrometric (GC-MS) method is proposed for pesticide multiresidue analysis of apples. The QuEChERS method was used for sample preparation. GC-MS analysis was performed with a PTV, an autoinjector, and a quadrupole benchtop MS detector. Electron-impact ionization (70 eV) was used with two modes of selected ion monitoring. Compounds were separated under temperature-programmed conditions on a narrow-bore diphenyldimethylsiloxane column. In one chromatographic run 61 pesticides of different chemical classes, and triphenyl phosphate as internal standard, were determined in 11 min. Calibration was performed with matrix-matched standard solutions and response to the pesticides was a linear function of concentration in the range 1-500 ng mL(-1) (equivalent to 1-500 mu g kg(-1) in real samples). High values of the determination coefficients (R-2; 0.9900-1.0000) were obtained for most of the pesticides. Limits of detection and quantification were determined. When the method was used for analysis of pesticide residues in real samples, five pesticides were detected at concentrations in the range 1.00-21.47 mu g kg(-1). Repeatability of measurements, expressed as relative standard deviations of absolute peak areas, normalized relative to TPP, and of the concentrations determined, met the EU criterion of RSD 20%. Use of the internal standard moderately improved quantitative results.