Comprehensive evaluation of the clean-up step in QuEChERS procedure for the multi-residue determination of pesticides in different vegetable oils using LC-MS/MS

Abstract

In this study the analytical performance of three QuEChERS-based sample preparation procedures for multi-residue pesticide analysis were evaluated on four different vegetable oil matrices (olive oil, sunflower oil, palm oil and rapeseed oil) by LC-MS/MS. Different combinations of PSA (primary secondary amine), C₁₈ and GCB (graphitized carbon black) sorbents were studied for the selected matrices in an effort to find out the most suitable clean-up approach for the selected types of vegetable oils. The effects of the different level on clean-up were evaluated by monitoring the method performance main parameters (recovery values, matrix effects and limits of detection) for a group of 44 relevant pesticides important in the cultivation of oil plants. From the aspect of matrix effects and LOD studies, the PSA + C₁₈ + GCB sorbent-combination was the most suitable for the analysis of vegetable oils, since this method provided the lowest matrix effects and good LODs. However, when this method was applied, poor recovery was achieved (only 16% of the recovery results were acceptable), as the GCB sorbent adsorbed a remarkable part of the analytes. When GCB was omitted, good recoveries were obtained from all the four vegetable oil matrices tested (91% of results were acceptable) with good reproducibility, indicating that the effectiveness of the clean-up step should be sacrificed to obtain adequate recoveries. The further exclusion of C₁₈ sorbent remarkably decreased the method performance in the case of palm oil and rapeseed oil, indicating that the PSA + C₁₈ combination should be applied, while the applied quantity of GCB sorbent should be carefully adjusted.