Determination Of Waste Cooking Oil By Activated Carbon Fiber-solid Phase Microextraction Coupled To GC-MS

Recent years, the crimes about waste cooking oil are common occurrence. The wasteoil contains a variety of poisonous and harmful impurities, microorganism, and heavymetal ions, low nutritional value. Due to its carcinogenicity, eating the waste oil would doharm to the people’s health. There are many detection methods of gutter oil, such as acidvalue, peroxide value, near infrared reflection (NIR) technique method, nuclear magneticresonance method and so on. Although these methods obtained some achievements, thereare some shortages restricting their wide application because of the complexity of wasteoil. It is of important significance to establish an efficient and effective method for thedetection of the illegal waste cooking oil.Solide-phase microextraction (SPME) technology is an all-in-one technology whichcontains sample extraction and concentration with high sensitivity, strong selectiveand the operation simplicity. Activated carbon fiber (ACF) is a novel adsorption materialwith strongly heat-resistant, high strength, stability, wide adsorption range. ACF-SPMEtechnology has been used in the field of food detection, marine pollutant detection, etc.This paper based on ACF-SPME and GC-MS to detect and analyze the volatilecomponents in waste cooking oil.After the experiments, the optimum extraction condition is0.0250g sample,0.0050gNa2SO4, extraction at120C for50min, and desorption for1min. The samples weretaken from different areas such as Taizhou in the Zhejiang province, Xiaoshan district in the city of Hangzhou, and sunflower oil, peanut oil, soybean oil of different brands. Compared the volatile composition of oil, there were13more substances in gutter oil than that of sunflower oil,8more than peanuts oil and10more than soybean oil. These substances are primarily ketone, aldehydes and esters. When the vegetable oil was heated at different temperature and for different time, there are some esters and hydrocarbon appeared in the oil. Several of them also existed in the gutter oil. Therefore, these substances were used as the characteristic components of the gutter oil.The experiments measured the waste oil from different sources and different brands of plant oil under optimal conditions. The results are that2-nonadecane ketone and heptanal can be detected in all oils, and we find the content of2-nonadecane ketone in drainage oil is much higher than that in plant oil; the content of heptanal and other materials is proportional to the increase and decrease. Then we put forward the M value to judge the illegal waste oil. The formula is as follows:M=(H2/H1)2, H2means the peak height of2-nonadecane ketone, H1means the peak height of heptanal. The results show that the M value of different brands of plant oil are all lower than40, while waste cooking oil is much higher than40, up to339.07. After the further experiments and analysis, we draw the conclusion that the2-nonadecane ketone in the waste oil mainly transfer and concentrate from animal fat oil in the process of repeatedly used. The method showed the suitability in analyzing the swill oil.Various of edible oils were heated at250℃for several times. The relationship between the content of specific material and heating times was analyzed and an A value was raised:. α(1) means the peak area increased with the increase of heating times,β(j) means the peak area reduced or remained with the increase of heating times, φ、ω means intensifying factor,γmeans normalization. The result showed that A increased with the heating times and the A values obtained in waste oil and frying oil were all higher than that of pure oils. For this instance, this method is appropriate for differentiating the waste oil but also the frying oil.The gutter oil was mixed with edible oil in different proportions respectively. According to the relationship between doping ratio and the chromatographic peak area of some substences, we proposed a T value calculation method:T=T’-T0, Apn means the peak area increased with the increase of doping ratio, Apm means the peak area reduced or remained with the increase of doping ratio, To means the T value of pure oil. The experimental result showed that the T value increased with mixed ratio and the figure obtained in the waste oil was much higher. Hence, this method could be used to judging the pure oil whether adding the waste oil.