Determination And Uncertainty Evaluation Of Four Synthetic Antioxidants In Food

Many foods, especially those high in polyunsaturated fats, are susceptible to lipid peroxidation, eventually leading to spoilage. Vitamins and pigments in food can be destroyed (thereby reducing their nutritional value), the food may became malodours and off-flavours. Formation of free radicals are danger to hunman being.Therefore, prevention of lipid peroxidation has long become an important issue,Among various modern methods to prevent lipid peroxidation, the addition of antioxidants is preferentially considered. Most of the commonly used antioxidants are synthetic compounds such as t-butyl-4-hydroxyanisole (BHA), 2,6-di-t-butyl-p-hydroxyto luene (BHT) and t-butyl hydroquinone (TBHQ) propyl gallate (PG) because of their chemical stability, low cost and availability.However, the synthetic antioxidants were not the content of the foods, besides there were many nonstandard operate in the food industry, the antioxidants in food were always out of standard. More and more results were proved that they were some side-effects for human being. Therefore, the contents of these synthetic antioxidants in foods should be carefully monitored.In this paper, 4 kinds of antioxidants, e.g. BHA, BHT, TBHQ and PG have been tested by HPLC (Diode-array Detector). In this method, we choose the conditions as following: the chromatographic column is C18 column, the temperature of column is 40°C, the flowing speed is 1ml/min, the quantity of sample injection is 20μL and wave length of testing is 280nm. The solid food sample is firstly dissolved by n-hexane, then extracted by methanol; the mobile phase is acidic water solution (1.5% acetic acid - water solution) and methanol. The adopted gradient elution program is: From 0 to 5min, the mobile phase is 70% ratio of acetic acid-water solution (A) and 30% of methanol (B). From 5 to 20 min., the ratio of mobile phase A is going down from 70% to 20%, and meanwhile, the ratio of mobile phase of B is going up from 30% to 80%. Keep this ratio of phase A and B, the sample is eluted from 10 min. Therefore, the complete isolations of four kinds of antioxidants are realized.The external standard method was adopted to the qualitative analysis and quantitative analysis. The lowest detection concentration of BHA, BHT, TBHQ, PG were 0.15mg/L, 0.25mg/L, 0.14mg/L, and 0.07mg/L. Their relative standard deviations were less than 10%, and the average recoveries were between 83.2% and 109.3%. The results show that this method is accurate and credible.Taken TBHQ as example, the uncertainty of the above method was investigated in the present study. The purity of standard material, constant volume V, sampling volume and repeatability affected the uncertainty and the resulting relative values were 0.000636, 0.0020, 0.0000072 and 0.0737, respectively. The synthetic standard uncertainty U (C) =k×u (C) =0.00512 (k=2). The repeatability during the sampling and analysis could significantly influence the final results.