| For the determination of contaminations in food, the most time-consuming and tedious step is the sample pretreatment. Gel permeation chromatography is a new developed method for the sample pretreatment. Good repeatability, high degree of automation, high efficiency of operation are the most obvious characteristics of GPC. The sample pretreatment can be simplified and the efficiency of analysis can be improved by GPC. GPC is widely used for separation and removal of proteins, lipids, pigments and other macromolecules.Chloropropanols are a group of chemicals which can be found in a wide range of foods and ingredients, most notably in soy sauce and related products. It has been reported that chloropropanols are carcinogenic, and to affect kidney functioning, fertility and nervous system. In view of this, many countries set strict limts of chloropropanols in food. Due to the complicated ingredients in soy sauce, good effect can not be achieved by the general sample pretreatments. Nowadays, matrix solid phase dispersion(MSPD) is widespread used for the pretreatment of chloropropanols. The operation of MSPD is time-consuming, tedious and less efficient. Besides, it costs a large number of organic reagents, which is harmful to the health of operators and environmental protection. Therefore, based on the sample pretreatment problem of chloropropanols and the advantages of GPC, study on how to use GPC to develop an efficient, fast and easy pretreatment method was done.Phthalate esters (PAEs) are widely used as plasticizers in food packing materials. Phthalate esters are recognized as environmental endocrine disruptors because of their potential to elicit reproductive and development toxicity. Because of its lipophilic characteristic, contamination of foodstuffs by PAEs can occur as a result of food-contact packing. Generally, plastic drums are used as containers of edible oil. It’s possible for PAEs to migrate into edible oil to threaten human health. It’s eseential to determination the contents of PAEs in edible oil. For oil samples, GPC is a good method for purification.In this paper, methods were developed for the dermination of chloropropanols in soy sauce and PAEs in edible oil. GPC was used as a pretreatment method. Gas chromatography mass spectrometry combined with the stable isotope technique was used as a determination method. The validation of this method was done, comparing with the current national standard methods. The main conclusions of this paper as followed:(1) GPC was developed as a pretreatment method of chloropropanols including1,3-DCP、2,3-DCP、3-MCPD in soy sauce. Sample portion(5g soy sauce),6g diatomaceous earth was added and mixed,50mL ethyl acetate as extraction solvent, extraction by shaking30min. Ethyl acetate-cyclohexane (1:1,V:V) was used as mobile phase. The eluted portions of9-14min were collected. In this condition, macromolecule such as proteins, lipids in samples can be removed by GPC efficiently, recoveries were in the range of94.62%-113.15%.(2) Study on the conditions of chromatography and mass spectrometry of chloropropanols was optimized. TG-5MS was chosen as the column, the oven temperature was started at50℃and held for1min; then increased to90℃at a rate of2℃/min; then increased to250℃at a rate of40℃/min and was held for5min. Gas chromatography mass spectrometry combined the stable isotope technique was used as the detection method. The selected ions used for identification and quantitation by SIM mode were shown in Table9. The linear detection range were0.010-2.000μg/mL. The detection limits were0.0050μg/mL(1,3-DCP),0.0070μg/mL(2,3-DCP),0.0060μg/mL (3-MCPD). Recoveries were in the range of84.08%-117.42%in spiking experiments. The results showed that repeatability expressed as RSD values were3.54%-7.95%. There were no significant differences between the new method and national standard method.(3) GPC was developed as a pretreatment method of PAEs including22kinds in edible oil. Sample portion(0.2g edible oil), Ethyl acetate-cyclohexane(1:1,V:V) was used as extraction and elute reagents. Ethyl acetate-cyclohexane(1:1,V:V) was added to set the volumn to10mL, after through the membrane, the extract is used for GPC purification. The eluted portions of9-15min were collected. In this condition, recoveries were in the range of100.11%-118.72%, meeting the requirements of pretreatment.(4) Study on the conditions of chromatography and mass spectrometry of PAEs was optimized.The suitable column, temperature programming and selected ions were studied. DB-17MS was chosen as the column. The oven temperature was started at60℃and held for1min; then increased to150℃at a rate of20℃/min and held for1min; then increased to280℃at a rate of3℃/min and was held for10min. DBP-d4, DEHP-d4, DINP-d4were chosen as the internal standard combined gas chromatography mass spectrometry as detection method. The selected ions used for identification and quantitation by SIM mode were shown in Table17. The linear detection range were0.020-2.000μg/mL(DMP etc.19kinds),0.10-10.00μg/mL (DINP etc.3kinds).The detection limits were0.05180mg/kg-0.9466mg/kg. Recoveries were in the range of88.30%-120.86%in spiking experiments. The results showed that repeatability expressed as RSD values were0.93%-10.53%. There were no significant differences between the new method and national standard method.(5) The methods were used to monitor real samples. Of20soy sauce sampls,5samples were detected chloropropanols, but the contents are below the EU limits. Of30soy sauce samples, DMP、DIBP、DBP、DEHP in5samples were found. According to national limts of PAEs,3samples were beyond the limts. The reasons may be migration from packing materials during production, storage, and transport of foodstuffs. |
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