Simultaneous Determination of Neonicotinoid Insecticides and Metabolites Residues in Milk and Infant Formula Milk Powder by EMR-Liquid Chromatography-Tandem Mass Spectrometry

Abstract

Abstract An analytical method based on Enhanced Matrix Removal Lipid - Liquid Chromatography - Tandem Mass Spectrometry (EMR-LC-MS/MS) was developed for determination of neonicotinoid insecticides and metabolites residues (Imidacloprid (IMI) and its metabolites Imidacloprid-urea (IMI-U), Imidacloprid-olefin (IMI-O), Acetamiprid (ACE) and its metabolite N-desmethyl acetamiprid (IM 2 − 1), Dinotefuran (DIN) and its metabolite [1-methy1-3(tetrahydro-3-furylmethy1) urea (DIN-UF), Thiacloprid (THIA), Thiamethoxam (TMX), Clothianidin (CLO, metabolite of thiamethoxam), and Flupyradifurone (FLU)) in milk and infant formula milk powder. In this method, samples were added with extraction kits (containing sodium chloride, anhydrous magnesium sulfate, sodium citrate and sodium hydrogencitrate sesquinydrat), and acetonitrile was used for the protein precipitation and extraction, and then cleaned up by EMR, detected by LC-MS/MS with multiple reaction monitoring (MRM) mode under positive electrospray ionization (ESI+), the isotope dilution internal standard or external standard method were used for quantification. The limits of quantification (LOQs, S/N = 10) were 2 µg/kg (IMI, IMI-U, ACE, IM 2 − 1, DIN-UF, THIA and TMX) and 5 µg/kg (IMI-O, DIN, CLO and FLU) for milk; 2 µg/kg (ACE), 15 µg/kg (THIA, IM 2 − 1, DIN-UF, THIA and TMX) and 40 µg/kg (IMI-U, IMI-O, DIN, CLO and FLU) for infant formula milk powder. The five levels calibration curves were used for quantification (0 µg/kg, 5 µg/kg, 10 µg/kg, 50 µg/kg, 100 µg/kg for milk and 0 µg/kg, 40 µg/kg, 80 µg/kg, 400 µg/kg, 800 µg/kg for infant formula milk powder), the correlation coefficients of linear calibration curve were higher than 0.995. At three spiked levels of 5, 10, 50 µg/kg (milk), or 40, 80, 400 µg/kg (infant formula milk powder), the recoveries were in the range of 71.7–108.7% and 71.9%-107.1%, the relative standard deviations were below 12.6% and 13.9%, respectively. This method was simple, rapid, and accurate to determinate the neonicotinoids and their metabolites residues in milk and infant formula milk powder.