Rapid Determination of Residues of Fenpropathrin Enantiomers in Fruit Puree of Infant Dietary Supplement by Ultra-High Performance Convergence Chromatography

Ethyl acetate (20 mL) and 3.0 g of sodium chloride were added into 5 g of fruit puree of infant dietary supplement sample. The mixture was vortexed for 1 min, and centrifuged for 5 min. The extraction was repeated once with 20 mL of ethyl acetate. The two supernatants were combined and evaporated to near dryness under vacuum at 40℃. The residue was dissolved in 5 mL of methanol. The solution was passed through the activated C₁₈ solid phase extraction column, and the entire effluent was collected, and dried to near dryness by nitrogen at 40℃. Then 1 mL of heptane was added, and vortex process was made for 1 min to dissolve the residue. The solution obtained was filtered through a 0.22 μm organic phase filter membrane, and the filtrate was analyzed by UPC². Acquity Trefoil AMY1 column was used as the stationary phase. Mixed solutions composed of methanol solution containing 0.5% (φ) ammonia and supercritical carbon dioxide at different volume ratios were used as the mobile phase for gradient elution. (-)-Fenpropathrin and (+)-fenpropathrin were determined by external standard method at detection wavelength of 230 nm. It was shown that linear relationships between values of the mass concentration and peak area of the fenpropathrin enantiomers were kept in the range of 1.0-20.0 mg·L^-1, with lower limits of determination (10S/N) of 0.2 mg·kg^-1. The spiked recovery test was made at three concentration levels on the negative fruit puree samples, giving recoveries of the 2 targets in the range of 81.4%-106%, and RSDs (n=6) of the determined values in the range of of 4.1%-7.2%. The proposed method was used for the analysis of 20 fruit puree samples, and (-)-fenpropathrin (0.25 mg·kg^-1) and (+)-fenpropathrin (0.22 mg·kg^-1) were detected in one pear puree sample.