Researches On Determination And Migration Of Phthalic Acid Esters In Food And Food Packing Materials

Five kinds of phthalic acid esters (PAEs), including Dimethyl phthalate (DMP), Diethyl phthalate (DEP), Di-n-butyl phthalate (DBP), Di-2-ethylhexyl phthalate (DEHP), di-n-octyl phthalate (DOP) were systematically investigated by gas chromatography in the present thesis with the purpose of establishing the simultaneous analysis method of above environmental hormone. And the resulting method was used to determine the content of five phthalates in ten kinds of plastic bags for food use in the market as well as in fourteen kinds of foods widely consumed in daily life.The optimum operating conditions of GC-FID for PAEs detection was obtained as follows: A HP-5 capillary column (30.0 m×320μm i.d.) coated with 0.25μm film was employed for separation of the analytes. The oven temperature was programmed elevation from initially 150℃for 1 min, then increased to 240℃at 60℃/min and held 1 min, finally reached 260℃at 40℃/min and kept 5 min. Nitrogen served as carrier gas at a flow rate of 2.5 mL/min. The injector and detector temperatures were set at 250 and 300℃, respectively. The injected volume of liquid samples was 1μl.The solid-phase extraction (SPE) procedure is a new short time-consuming and economical sample pretreatment technique. LC-Si columns were applied to investigate the effect of different factors including eluent agents, elution volume and elution rate on extraction efficiency of various samples. The best parameters of SPE for PAEs were obtained: ethyl acetate as eluent and elution volume of 3 ml, elution rate at 1 mL/min.The thesis established the analytical procedures of PAEs present in food and packing materials based on the ultrasonic extraction and solid-phase extraction. The average recoveries of five phthalates in the plastic products for food ranged from 80.3%-95.5%, and the relative standard deviations (RSDs) were from 0.25%-2.89%, indicating this method was accurate and credible.Edible oil and seedcake were selected to investigate the migration of PAES from food packing to food. The experimental design was as follows:(1) Edible oil was stored under different conditions (temperature, packing materials, and storage time) and the content of PAEs was determined at the end of storage period. The results indicated:a. Various plastic bags contained different concentrations of the phthalates. The higher in plastic, the more in the food.b. The migration of PAEs from plastic bags into food was increasing as temperaturerise.c. There was significant correlation between the migration of PAEs into food and storage time. The content of PAEs in food vary significantly with time prolonged.(2) Seedcake was packed into three plastic bags of 30 g per bag when it's warm, cold and microwave heating 2 min after packing, respectively and the content of PAEs was determined after 0.5 h storage. The results showed that the content of DEHP were close in packing when it's warm or cold, whereas higher content of DEHP was present in microwave-treated group. All the results indicated that microwave treating of the plastic packaged food could be able to accelerate the migration of phthalates from plastic bags into food.