Potential Applications of HS-SPME/GC in Oxidized Vegetable Oils

Headspace solid phase microextraction chromatography (HS-SPME/GC) was evaluated as a tool in determining the rate of oxidation in oxidized soybean oil samples by measuring the production of hexanal as a secondary major volatile breakdown product of linoleic acid. Samples of the headspace taken from sealed 20 mL vials, incubated 30 min at 50 °C followed by 5 min adsorption, were injected into a gas chromatograph with 2 min thermal desorption. In applying SPME, different analytical conditions were evaluated. The linearity of response of the volatiles for the HS-SPME/GC procedure using a carboxen-polydimethylsiloxane fiber was determined from 3 g of mineral oil spiked with a hexanal standard solution at different levels. Using the optimized extraction conditions, an R value close to unity (R = 0.999) was found, and the repeatability (n = 11) was 6.31%. The results indicated that hexanal is linearly related to peroxide value (PV) only intermediate PV ranges (10-18 meq/kg). The study also showed that HS-SPME/GC procedure was a simple and reproducible method for the analysis of hexanal in the HS of commercial soybean oil samples, and is useful as a quality control and research tool for the evaluation of flavor quality and shelf life of vegetable oils.