| Background Phthalic acid esters(PAEs) is a kind of plasticizer commonly used, which can increase flexibility and strength of the plastic, so PAEs is widely used in plastic industry. PAEs is harmful to human body health, can affect the body’s endocrine function, is called the "environmental hormones". Ago, plasticizer detection are mainly concentrated in the plastic containers and plastic packaging materials, but in recent years, some unscrupulous traders added plasticizer according to its plasticizing characteristic instead of cloud agent and emulsifier to food, even medicine, therefore, the detection of plasticizer in food has the important meaning.Purpose Quantitative determination method of six kinds of phthalic acid esters plasticizer in the water by HPLC was established and pretreatment method to optimize phthalic acid ester in the water. To detect the content of plasticizer in drinking water in daily life and several drinks from a few supermarkets, at the same time to explore the influence of temperature on plasticizer release.Method Using liquid-liquid extraction and ultrasonic extraction method to centrifuge and extract six kinds of phthalic acid esters in the water, including dimethyl phthalate(DMP), diethyl phthalate(DEP), butyl phthalate(DBP), phthalate amyl(DAP), phthalate(2- ethyl hexyl) ester(DEHP) and phthalate esters(DOP),and along with method of rapid centrifugal to get rid of impurities. Two kinds of mobile phase elute according to proportion, which respectively for methanol/water as 80:20, methanol/water as 95:5, column temperature is 30℃, using C18 reverse phase column to separate the material under test.Results 1. The choice of chromatographic conditionsThis study adopted HPLC method to detect six PAEs kind of plasticizer, according to the physical and chemical properties of PAEs, chose C18 column, separated six PAEs kind of plasticizer. Stationary phase of reverse phase chromatography is the nonpolar substance which is suitable for separation of polar substance, so we chose reversed phase C18 column in the selection of chromatography column.Through the sample analysis of six kinds of reference substance, we observed absorption peaks of phthalic acid esters in 228 nm, 242 nm, 245 nm, 280 nm. The results showed that there was good peak shape in 245 nm, so we chose 245 nm as detection wavelength.Using a single eluent of methanol/water as 95:5 is not effective to separate of six kinds of substance, and the separation time is too long with methanol/water as 80:20. Therefore, this study adopted two kinds of mobile phase elution, respectively for methanol/water as 80:20, methanol/water as 95:5, to separate the six kinds of substance. The results showed that the elution method can quickly separate six kinds of PAEs plasticizer.2. The linear range and detection limitThe DEM, DEP, DBP, DAP, DEHP and DOP with chromatographic conditions set in this study had good linear relationship in 0.25 ~ 10μg/L, and the correlation coefficients were above 0.999. With the material under test concentration of three times the noise as the minimum detection limit, the detection limit of DBP was 0.07μg/L, the detection limit of DOP was 0.20μg/L, the detection limit of DEHP was 0.14μg/L, the detection limit of DMP was 0.17μg/L, the detection limit of DEP was 0.22μg/L, the detection limit of DAP was 0.09μg/L.3. Recovery rate and precisionTo operate at the set conditions, taking 0.01μg/ml mixture under the same conditions to sample repeated six times and average the results, measuring its recovery rate and precision. The results showed that the recovery rate of six kinds ofPAEs plasticizer were above 79.4%, the relative standard deviation(RSD) < 0.87%, the precision was good.4. The stabilityThrough measuring the content of six kinds of PAEs after placed 0, 3, 12, 24, 48, 60 hours, we examined its stability. The results showed that the RSD of six kinds of PAEs after placed 0, 3, 12, 24, 48, 60 hours were <0.38%, its stability was good.5. The test results of samplesWe tested eight kinds of samples according to the above method, among them mineral water, coffee, yogurt drinks and yogurt had six batches respectively, double steaming water, plastic cup water, plastic bottled water and tap water respectively sampled six times for testing analysis, and averaged the content of PAEs. The results showed that there were no the PAEs plasticizer in the mineral water, yogurt and double steaming water, the content of DMP in coffee is 2.955μg/L; the content of DMP in yogurt drinks is 0.443μg/L; the content of DBP in plastic bottled water is 9.210μg/L and the content of DEHP is 1.511μg/L; the content of DBP in plastic cup water is 7.312μg/L.In order to further investigate the influence of temperature on the dissolution of PAEs plasticizer, we according to the above experiment method respectively tested 20 mineral water heated an hour, 40℃mineral water heated an hour, 40℃mineral water heated two hours and 40℃mineral water heated four hours. Repeated six times for testing analysis, and averaged the content of PAEs. The results showed that there were no the PAEs plasticizer in the 20℃mineral water heated an hour; the content of DBP in the 40℃mineral water heated an hour is 1.1μg/L; the content of DBP in the 40℃mineral water heated four hours is 0.8μg/L and the content of DOP is 2.3μg/L.ConclusionThere was a higher recovery rate with using n-hexane to extract PAEs plasticizer.1. With methanol/water as mobile phase, column temperature 30 ℃, reversed-phase C18 column as chromatographic column to separate PAEs plasticizer in water, there was good linear, high precision and accuracy, correlation coefficients were above 0.9994, the method can be used for batch sample detection of PAEs plasticizer.2. Bottled water of long time exposure, inferior plastic cups and coffee drinks contained PAEs plasticizer.3. Temperature can increase the dissolution of PAEs plasticizer. |
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