| Food safety is closely bound up with public life. Phthalate esters(PAEs) and chlorophenols(CPs) as main environmental estrogens studied in this study widely exist in people’s daily diet, i.e. fatty food and alcoholic beverages. Owing to the diverse polarity of PAEs and their ubiquity, it was difficult to extract and detect all of them. CPs not only have higher polarity, but also occur in a very low concentration in real samples, resulting in low extraction efficiency using conventional sample pretreatment methods. To solve above problems, determining total PAEs was selected to reduce the effect from reagent blank and polluted samples, which not only largely improve the accuracy of analysis results, but also could act as supplementary means of preliminary evaluation of PAEs pollution degree in food and sample screening method before determining individual PAE; new type of extractants based on molecular complex in DLLME was used to obtain high extraction efficiency for high polar analytes and reduce the matrix effect; combination of extraction techniques was introduced to improve the enrichment factor, achieving the trace analysis of CPs in samples.Therefore, this work mainly studies novel sample pretreatment methods for the determination of PAEs and CPs in food. The specific research content is divided into the following three parts:1. A series of fast, accuracy and environmental methods for the determination of total PAEs in different matrices(high-fat foods and beverages) were successfully developed. These methods include extracting PAEs from matrix using LLE(or DLLME), converting PAEs to phthalate acid(PA) with TBAB-catalyzed alkaline hydrolysis, extracting PA with DLLME and aqueous alkali back-extraction, and detecting PA via high performance liquid chromatographydiode array detector(HPLC-DAD). One notable feature of this study was that according to the complexity of matrix, suitable liquid extraction methods were used to extract a variety of PAEs. Another significant innovation was that TBP was selected as a new type of extractant based on molecular complex and THF was selected as a partitioned DLLME disperser used to extract PA, which achieved a satisfactory extraction result. Under the optimum conditions, the calibration plot of PA was found to be linear in the range of 0.1~5 μg/m L, with a correlation coefficient(r2) of 0.9996; the LOD and LOQ were 3.14~20.91 and 10.45~69.69 ng m L-1. These methods were successfully applied to 13 meat products, 17 milk products, 12 beverages, 3 condiments and 8 snacks. Results showed that PA concentration in beverages(except for white spirit) could be negligible and the PA concentration was increased in food as the following order: milk products(0~3.56 nmol m L-1) < meat products(0~7.03 nmol g-1) < snacks(0~8.68 nmol g-1) < condiments(0~17.98 nmol g-1) < white spirits(3.03~32.67 nmol m L-1).2. A very simple, fast and environmentally friendly sample extraction method was proposed for the analysis of four PAEs in alcoholic beverages by using conventional ionic liquid dispersive liquid–liquid microextraction(IL-DLLME). The samples were extracted by 160 μL 1-octyl-3-methylimidazolium hexafluorophosphate; the enriched analytes in sedimented phases were analyzed by HPLC-DAD. Under the optimum conditions, a satisfactory linearity(in the range of 0.02~1 μg m L-1 for white spirits and 0.01~0.5 μg m L-1 for red wines with the correlation coefficients(r2) varying from 0.9983 to 1), acceptable recovery rates(88.5~104.6%), good repeatability(RSD≤8.0%) and low detection limits(3.1~4.2 ng m L-1 for white spirits and 1.5~2.2 ng m L-1 for red wines) were obtained. The developed method was successfully applied for the determination of the four PAEs in 30 white spirits and 11 red wines, and the DBP content detected in 63% white spirits exceeded the specific migration limit of 0.3 mg kg-1established by international regulation.3. A novel procedure of sample preparation combined with HPLC-DAD is introduced for the analysis of seven highly chlorinated phenols in wine. The main features of the proposed method are(i) low-toxicity diethyl carbonate as extraction solvent to selectively extract the analytes without matrix effect,(ii) the combination of salting-out assisted liquid–liquid extraction and DLLME to achieve an enrichment factor of 334~361, and(iii) the extract is analyzed by HPLC to avoid derivatization. Under the optimum conditions, correlation coefficients(r2) were >0.997 for calibration curves in the range 1~80 ng m L-1, detection limits and quantification limits ranged from 0.19 to 0.67 and 0.63 to 2.23 ng m L-1, respectively, relative standard deviation was <8%, and recovery rates were in the range 82~104%. The method was applied for the determination of chlorophenols in real wines, and found that they were free of the CP, or at least beyond the corresponding LOQs. |
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