Multi-residue method for determination of 238 pesticides in Chinese cabbage and cucumber by liquid chromatography-tandem mass spectrometry: comparison of different purification procedures.

This paper describes the comparison of five sample cleanup procedures for the determination of 238 pesticides via triple quadrupole liquid chromatography-tandem mass spectrometry (LC-MS/MS, with only 10 min of chromatographic running time) in Chinese cabbage and cucumber. Samples were extracted with a quick, easy, cheap, effective, rugged, and safe (QuECHERS) preparation method and cleanup with different sorbents, including primary secondary amine (PSA), multi-walled carbon nanotubes (MWCNTs), and polystyrene (PLS), to find out the most suitable cleanup methods for Chinese cabbage and cucumber. The recovery and matrix effect were evaluated by monitoring the main parameters in one group of 238 pesticides at the spiked level of 8 and 40 μg/kg. In Chinese cabbage, when PSA dispersive solid-phase extraction (D-SPE) was applied, recoveries of 183 pesticides ranged between 70 and 120% with relative standard deviation (RSD) values lower than 20% at a spiked level of 40 μg/kg, indicating the effectiveness of the purification step. In cucumber, 203 pesticides were in the 70-120% recovery range with good reproducibility by PSA mini-cartridge column cleanup at a spiked level of 40 μg/kg and RSD values were generally below 20%. The limits of quantitation [LOQs; signal-to-noise (S/N) = 10] were in the range of 0.16-10.20 μg/kg for Chinese cabbage and 0.06-21.06 μg/kg for cucumber, while the limits of detection (LODs; S/N = 3) were between 0.05 and 3.06 μg/kg and between 0.02 and 6.32 μg/kg in Chinese cabbage and cucumber, respectively. The proposed methods that might be applied for the multi-residue analysis in Chinese cabbage and cucumber are contributed to their rapid speed and good recoveries.