Optimisation of programmable temperature vaporizer-based large volume injection for determination of pesticide residues in fruits and vegetables using gas chromatography-mass spectrometry.

The applicability of programmable temperature vaporizer (PTV) solvent vent injection to the gas chromatographic (GC) determination of pesticide residues in fruits and vegetables was evaluated with the aim of miniaturizing the current multiresidue method. For that purpose 24 pesticides representing different chemical classes were initially chosen for optimisation of the large volume injection (LVI) parameters. Various parameters related to the optimum injector performance were tested for several types of packed and empty liners using both fast (at-once) and speed-controlled PTV solvent vent injection of standard solutions in ethyl acetate. In the next step, several packed and empty liners were evaluated for their suitability for pesticide multiresidue analysis. Parameters identified as optimal were then applied for PTV solvent vent injection of sample extracts prepared using the miniaturized multiresidue method to assess the long-term stability of the system. The combined use of large volume injection of 10 microl ethyl acetate extract into an empty multi-baffled or a CarboFrit packed liner using PTV injectors and GC-MS analysis enabled the detection and quantification of 124 pesticides in fruit and vegetable samples at the 0.01 mg/kg level using miniaturized reversed-phase solid-phase extraction (RP-SPE) of diluted acetone extract and clean-up on a small anion-exchange SPE column.