Development of QuEChERS-DLLME method for determination of neonicotinoid pesticide residues in grains by liquid chromatography-tandem mass spectrometry

Monitoring neonicotinoid residues in grains is of significant interest for the proper assessment of pesticide exposure to human. The quick, easy, cheap, effective, rugged, and safe extraction method combined with dispersive liquid-liquid micro-extraction (QuEChERS-DLLME) was developed for extracting, purifying, and concentrating seven common neonicotinoid pesticides from the grains (rice, millet, and maize). Water and acetonitrile were used in tandem as extractants in QuEChERS, while water, acetonitrile, and trichloromethane in DLLME acted as the external phase, dispersant, and extractant, respectively. Comprehensive consideration of the single factor test and response surface method to optimize parameters including type and volume of extractants and dispersant. The evaluation showed that the QuEChERS-DLLME method held excellent linearity (R-2 > 0.99). The limits of quantitation ranged from 0.003 to 0.08 mu g kg(-1) for the seven insecticides. The recoveries were in the range of 62-118%, and good reproducibility was obtained with a relative standard deviation below 15%.