Sample preparation of cooking oils for determination of polycyclic aromatic hydrocarbons by high performance liquid chromatography

Abstract

Two sample preparation techniques, low-temperature cleanup and sweep co-distillation, which are simple, fast, inexpensive and using small amount of organic solvent have been developed for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) in refined and used cooking oil samples by high-performance liquid chromatography with fluorescence detection (HPLC-FLD). For low-temperature cleanup method, freezing time, extraction solvent, number of extraction and SPE cleanup affected the extraction efficiency. Optimum extraction was achieved when using a mixture of acetonitrile and acetone (80:20, v/v) as extraction solvent, freezing between -18 oC to -25 oC for 24 hours twice and cleanup with alumina N SPE cartridge. This method was effectively determined all 16 PAHs. The recoveries were 45.88 – 118.47%. Limit of detections (LODs) and limit of quantitations (LOQs) were 0.13 to 3.13 ng/g and 0.25 to 6.25 ng/g, respectively. In sweep co-distillation method, distillation temperature and time had an effect on the extraction efficiency. Optimum extraction was attained when distillated at 235 oC for 60 minutes. However, this method was quantitatively analyzed only 8 PAHs. The recoveries were 47.48 – 119.47%. LODs and LOQs values were about two times higher than low-temperature cleanup method. Finally, both methods were successfully tested for determination of PAHs in reference materials of olive oil (RM FAPAS T0631) and real cooking oil samples.