Determination of eight novel succinate dehydrogenase inhibitor fungicides in vegetables and fruits by modified QuEChERS

A method was developed for the simultaneous determination of eight novel succinate dehydrogenase inhibitor fungicides (boscalid, penflufen, bixafen, sedaxane, fluopyram, penthiopyrad, isopyrazam, fluxapyroxad) residues in vegetables and fruits by liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with modified QuEChERS. The amount of the two solid phase extraction agents (octadecyl bonded silica (C-18) and primary secondary amine (PSA)) in QuEChERS method was optimized according to their adsorption and purification capacities. The eight compounds were extracted from samples by acetonitrile and purified by solid phase extraction agents. The eight compounds were separated on a Poroshell 120 EC-C-18 column by the gradient elution using acetonitrile-0.1% (v/v) formic acid aqueous solution as mobile phases, detected by MS/MS with positive/negative electrospray ionization (ESI+-ESI-) in multiple reaction monitoring (MRM) mode, and finally quantified by external standard method. The correlation coeffcients (r) of the eight compounds were all above 0. 998 in the mass concentration ranging from 0. 5 to 500. 0 mu g/L. The limits of detection and the limits of quantification of the method were 0. 2-1. 7 mu g/kg and 0. 5- 5. 0 mu g/kg, respectively. The recoveries of the eight analytes spiked at three levels (5. 0, 25. 0 and 125. 0 mu g/kg) in eight matrices ranged from 71. 4% to 121. 3% with the relative standard deviations (RSDs, n = 6) from 0. 8% to 17. 2%. The method is easy to operate and with good purification effect. It can be applied to the rapid determination of the novel succinate dehydrogenase inhibitor fungicides in vegetables and fruits.