Determination of meptyldinocap residues in vegetable and fruit by liquid chromatography-tandem mass spectrometry

Abstract

A method was developed for the determination of the residues of meptyldinocap (2,4-dinitro-6-(1-methylheptyl) phenyl crotonate, 2,4-DNOPC) as 2, 4-dinitrooctylphenol (2,4-dinitro-6-(1-methylheptyl) phenol, 2,4-DNOP), which is a hydrolysate of 2,4-DNOPC, in six vegetable and fruit by using liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). The residues of 2,4-DNOPC in vegetable and fruit samples were extracted by the mixture of acetone, methanol and hydrochloric acid, then extracted by liquid-liquid partitioning, hydrolyzed under alkaline condition with ultrasonication, and extracted again by liquid-liquid partitioning, then analyzed by using LC-MS/MS in multiple reaction monitoring (MRM) mode via negative electrospray ionization with an Agilent ZORBAX SB-C, column. The method was validated at four fortification levels in vegetable and fruit. The validation results were as follows: the recoveries of 2,4-DNOPC in cabbages were from 89.7% to 93.3% (the relative standard deviations (RSD) of 6. 3% - 8.5%), in cucumbers from 87.7% to 95.1% (RSD of 5.8% -10.4%), in tomatoes from 89.3% to 96.0% (RSD of 6.8% -9.2%), in apples from 92.0% to 98.3% (RSD of 5.1% - 10.3%), in pears from 89.0% to 95.0% (RSD of 5.3% -10.2%), in grapes from 81.2% to 95.8% (RSD of 5.8% - 10.4%). The limits of quantification of 2,4-DNOPC in all the test samples were 0. 01 mg/kg. The results showed that the method is simple, rapid, and is characterized with acceptable sensitivity and accuracy to meet the requirements of the pesticide residue analysis. This method is applicable to confirm the residues of meptyldinocap in vegetable and fruit samples.