Determination of Oxidized Triacylglycerol Polymers by Preparative Flash Chromatography and High-performance Size-exclusion Chromatography

An simple operation and high sensitivity method without internal standard was developed for the quantitative analysis of oxidized triacylglycerol polymers(TGP).Polar compounds(PC) were obtained from 1 g oil sample by preparative flash chromatography(PFC)(flash silica column,20 g,particle size:40-60 μm,pore size:6 nm) and subsequently separated by a high-performance size-exclusion chromatography(GPC column,Φ7.8 mm×300 mm,particle size:5 μm,pore size:10 nm) into oxidized triacylglycerol polymers(TGP),oxidized triacylglycerol dimers(TGD),oxidized triacylglycerol monomers(ox-TGM),diacylglycerols(DG) and free fatty acids(FFA).By quantitation of PC in oil through gravimetric determination and TGP in PC through area normalization method,TGP content in oil was calculated.The results showed that the calibration curves for TGO and TGD were linear in the concentration ranges of 28-1 800 mg/L and 11-2800 mg/L,respectively,with correlation coefficients(r2) more than 0.99.Their LODs were 28 mg/L and 11 mg/L,respectively,and LOQs were 113 mg/L and 44 mg/L,respectively,which was equivalent to 0.01% for LOQ of TGP in oil.The RSDs of TGP in oil detected by PFC-HPSEC were less than 10%.The recoveries at spiked levels of 2.27%,8.47% and 30.94% ranged from 95% to 98% with RSDs less than 4%.In detecting TGP in oil,PFC-HPSEC matched traditional silica column well with RE of 0-8.9%.The method could be used in the determination of TGP in all kinds of oil samples,including used cooking oil and unused edible oil,especially for virgin oil and refined oils and fats with low levels of TGP.