Method validation of resistive heating—gas chromatography with flame photometric detection for the rapid screening of organophosphorus pesticides in fruit and vegetables

Abstract

A rapid method for the screening of organophosphorus (OP) pesticides in fruit and vegetables is reported. Sample extracts were analysed using resistive heating-gas chromatography (RH-GC) with flame photometric detection (FPD). A CarboFrit insert in the GC liner allowed injection of crude extracts onto the GC system. Separation of up to 20 pesticides was achieved in 4.3 min with excellent retention time stability. Signal-to-noise ratios of 5:1 or better were obtained for the majority of the pesticides at the lowest calibrated level (LCL), 0.01 μg ml−1, with excellent linearity over the range 0.01–0.5 μg ml−1 (0.004–0.2 mg kg−1 equivalent). Average recoveries between 70 and 116% were obtained for pesticides spiked at 0.01 and 0.1 mg kg−1 with associated R.S.D. values ≤20% in the majority of cases. Estimates of relative reproducibility standard deviation (R.S.D.R), made by combining observed R.S.D. values with estimates of uncertainty associated with mean recovery allowed the determination of HORRAT values which confirmed that the method is capable of producing results which are fit for purpose. The validated method was then used to screen peaches, grapes and sweet peppers for a total of 37 pesticides. Incurred residue results obtained using RH-GC–FPD were in good agreement with the results from analysis of the same samples using MS confirmation.