Optimization and validation of a method for the determination of acidic pesticides in cabbage and spinach by modifying QuEChERS procedure and liquid chromatography–tandem mass spectrometry

•QuEChERS CEN version was modified for determine 12 acidic pesticides in cabbage and spinach.•Carbopack Z, a high surface area graphitized carbon black, was used as sorbent material.•Carbopack Z and C18 mixture showed excellent matrix component removal ability in clean-up.•The extract was 10-fold diluted before LC-MS/MS injection, which reduced matrix effect efficiently.•The method was validated following SANTE/12682/2019 directions. A quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was developed and combined with liquid chromatography–tandem mass spectrometry to analyze 12 acidic pesticides in cabbage and spinach. The extraction solvents, phase partition salts and sorbents effect was studied to optimize the method followed by dilution before sample injection. The extraction involved 5% formic acid in acetonitrile, and the liquid-liquid partition was salt-induced. Carbopack Z, a high surface area graphitized carbon black, was a new sorbent used in the clean-up. The results show that Carbopack Z effectively removes interferences with little loss of acidic pesticides. All tested pesticide recoveries were satisfactory when Carbopack Z was combined with C18 in the clean-up at optimized condition. After clean-up, the extract was subjected to 10-fold dilution to sufficiently reduce the matrix effect (