Determination of Singlet Oxygen Generated in Vegetable Oil Using Furfuryl Alcohol as Trapping Agent

Singlet oxygen (O-1(2)), an initiator for photooxidation, is responsible for vegetable oil degradation. However, few details about the formation of O-1(2) in vegetable oil are known due to the lack of a reliable method for its determination. In this study, a simple, reliable, and sensitive high-performance liquid chromatography (HPLC) method for indirect quantification of O-1(2) generated in vegetable oil was developed. Furfuryl alcohol (FFA) was selected as a real-time "trap" for O-1(2). FFA was added to an oil sample, allowed to react with O-1(2), and the remaining FFA was subjected to two successive liquid-liquid extractions with 4 mL of acetonitrile. FFA concentration was then determined by reversed-phase HPLC with UV detection at 219 nm, and the rate of formation of O-1(2) was calculated from the quantitative reaction relationship between FFA and O-1(2). The method was validated, and the limits of detection and quantitation of FFA were 0.05 and 0.15 mu g/g of oil, respectively. The recoveries of FFA spiked at low, middle, and high concentrations ranged from 97.56 to 105.98%. The precision for determination of FFA in vegetable oil was <= 9.36% (intra-day) and 10.16% (inter-day). The approach was successfully applied to the analysis of O-1(2) generated in camellia oil, olive oil, soybean oil, and sunflower seed oil exposed to LED light (5000 lux) in the presence of methylene blue as photosensitizer (4.76 mu g/mL), and the formation rate of O-1(2) was 3.995 mu mol L-1 s(-1) to 4.299 mu mol L-1 s(-1).