Rapid Determination of Chloropropanol Ester and Glycidyl Ester in Diacylglycerol Oil by Gas Chromatography-Quadrupole Time-of-Flight Mass Spectrometry

The diacylglycerol oil sample （0.1 g） was taken and placed in a 2.5 mL-centrifuge tube, and 100 μL of 2.0 mg·L⁻¹ mixed internal standard solution was added. The mixture was vortexed to homogeneity, and 100 μL of toluene and 200 μL of methyl tert-butyl ether were added. After mixing, the mixture was cooled at 10 ℃ for 5 min, and 200 μL of methanol solution containing 0.35 mol·L⁻¹ sodium hydroxide was added. The mixture was vortexed for 30 s, and then settled at 10 ℃ for 12 min. 700 μL of acidified sodium bromide solution was added, and the mixture was vortexed for 30 s and settled at room temperature for 5 min. 600 μL of isooctane was added, and the mixture was vortexed for 2 min and centrifuged for 5 min. The isooctane layer was discarded, and the purification process was repeated once, and the lower aqueous phase was collected. 100 μL of 120 g·L⁻¹ phenylboronic acid solution was added, and the mixture was vortexed for 2 min, followed by the addition of 100 μL of 1% （volume fraction） ethylene glycol solution and 1 mL of isooctane. The mixture was vortexed for 1 min and centrifuged for 5 min, and the upper solution was taken, dehydrated with anhydrous sodium sulfate, and then filtered through a 0.22 μm organic phase filter membrane. The 2 chloropropanol esters, including 3-chloro-1,2-propanediol ester （3-MCPDE） and 2-chloro-1,3-propanediol ester, and glycidyl ester （GE） in the filtrate were determined by gas chromatography-quadrupole time-of-flight mass spectrometry. The 3 targets were separated on DB-5ms quartz capillary chromatographic column by programmed column temperature, ionized by electron impact ion source, and quantified by isotope internal standard method. As shown by the results, linear relationships between the ratios of the corresponding peak area to the internal standard peak area and the ratios of mass concentrations of 3 targets to their internal standards were found in the range of 0.100‒2.00 mg·L⁻¹, with the same detection limits （3S/N） of 0.06 mg·kg⁻¹. Test for recovery was made by the standard addition method, giving results in the range of 80.8%‒97.6%, with RSDs （n=6） of the determined values less than 10%. This method was applied to the analysis of 20 diacylglycerol oil samples, and 3-MCPDE and GE were detected in one rapeseed diacylglycerol oil sample, with the detection amounts of 0.335, 0.408 mg·kg⁻¹, respectively.