Simultaneous determination of 36 pesticide residues in spinach and cauliflower by LC-MS/MS using multi-walled carbon nanotubes-based dispersive solid-phase clean-up.

A multi-residue method based on a modified QuEChERS sample preparation with multi-walled carbon nanotubes (MWCNTs) as reversed-dispersive solid-phase extraction (r-DSPE) material and LC-MS/MS determination by MRM mode was validated for 36 representative pesticides in spinach and cauliflower. It was demonstrated that MWCNTs can be used as effective r-DSPE materials with the QuEChERS method for the clean-up of extract from different matrices. However, MWCNTs could absorb pyrimethanil, diflubenzuron, and chlorbenzuron in both spinach and cauliflower, which leads to the low recoveries compared with PSA. The LODs and LOQs for 36 pesticides ranged from 0.1 to 5 μg kg(-1) and from 2 to 30 μg kg(-1), respectively. Good linearity was found for all pesticides with coefficients better than 0.995 in a range of 0.02-0.5 mg l(-1). The developed method with MWCNTs clean-up was successfully used to determine the 36 pesticides in real samples.