Determination of Carbaryl in Meat and Meat Products by High Performance Liquid Chromatography-Isotope Dilution Tandem Mass Spectrometry with Gel Permeation Chromatographic Clean-Up

About 5 g (accurate to 0.01 g) of the sample and 50 μL of 1.000 mg·L^-1 carbaryl-D7 isotope internal standard solution were added into appropriate amount of water (1.5 mL of water for the meat sample, 3 mL of water for meat products). Then 40 mL of acetone was added and the mixture was homogenized for 1 min. 6 g of sodium chloride was added and the mixture was shaked well. 30 mL of petroleum ether was added and the mixture was shaked for 30 min and let stand for 30 min. The organic layer supernatant was taken, filtered through anhydrous sodium sulfate, and concentrated to about 1 mL by rotary evaporation. 2 mL of ethyl acetate-cyclohexane (1+1) solution was added, and the mixture was concentrated to about 1 mL by rotary evaporation. After the above operation was repeated 3 times, the solution was made to 10.0 mL with ethyl acetate-cyclohexane (1+1) solution, filtered through a 0.22 μm filter membrane, and cleaned up by gel permeation chromatography (GPC) under conditions as follow: Bio Beads S-X3 gel chromatographic column (400 mm×30 mm) was used as stationary phase, with ethyl acetate-cyclohexane (1+1) solution as mobile phase; fraction collection section was 10.0-15.0 min; on-line concentration heating temperature was 45 ℃; degree of vacuum was 2.0×10⁴Pa. After solvent replacement was carried out 2 times with acetonitrile as replacement solvent, the purified solution was made up to to 1.0 mL, and analyzed by liquid chromatography-tandem mass spectrometry. Separation was performed on a HSS T3 column (100 mm×2.1 mm, 1.7 μm) with a mixture of 0.1% (volume fraction) formic acid solution-acetonitrile (6+4) as mobile phase. Electrospray ionization source and multiple reaction mornitoring mode were used in mass spectrometry. Linear relationship was found between the ratio of peak area of carbaryl to peak area of internal standard with the mass concentration of carbaryl in the range of 0.010-0.500 mg·L^-1. The lower limit of determination (10S/N) was 0.005 mg·kg^-1. Values of recovery obtained by standard addition method were in the range of 81.0%-105 %, the relative standard deviations (n=6) of the measured values were between 3.8% and 16%.