Analytical Sciences

Determination of Hexanal as an Oxidative Marker in Vegetable Oils Using an Automated Dynamic Headspace Sampler Coupled to a Gas Chromatograph/Mass Spectrometer^¶

Jaeho HA,* Dong-Won SEO,* Xi CHEN,**,*** Jin-Bong HWANG,* and You-Shin SHIM*

*Food Analysis Center, Korea Food Research Institute, 516, Baekhyeon, Bundang, Seongnam, Gyeonggi, 463-746, Republic of Korea
**Department of Chemistry and the Key Laboratory of Analytical Sciences of the Ministry of Education, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
***State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China

An automated dynamic headspace sampler coupled to a gas chromatograph/mass spectrometer was evaluated as an oxidative marker to determine hexanal content in vegetable oils. For the effective analysis, a cooled injection system (CIS) was used to focus and to introduce the hexanal desorbed from the Tenax TA. The temperature of the CIS was maintained at −60°C for 12 min before desorbing the hexanal. Hexanal was separated on a capillary column (DB-5, 0.25 mm × 60 m, 0.25 μm in film thickness) from 50 to 230°C, followed by mass spectrometer-selected ion monitoring analysis at m/z 56. The instrumental response to hexanal was highly linear from 10 ng mL⁻¹ to 1 μg mL⁻¹ (r² = 0.9999). The relative standard deviation (RSD) of intra- and inter-day repeatability was acceptable, with values of less than 3.88 and 4.25%, respectively. The LOD and LOQ of hexanal were determined by gas chromatograph/mass spectrometer-selected ion monitoring to be 3.3 and 9.8 ng mL⁻¹, respectively. The acid value, peroxide value and fatty acid composition revealed a good correlation with the hexanal concentration.

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