Study On The Efficient Sample Pretreatment Technology For Determination Of Additives In Fatty Foods

In order to improve the color and lustre,fragrance and taste of food and prevent its corruption,food additives are usually added and vacuum packing bags（containing plasticizers）are used for storage.Fatty food,because of its high oil content and its easy corruption,need to add antioxidants and other food additives.The excessive intake of additives will harm the health of the human body,so it is very important to establish an efficient and accurate method for the analysis of additives.In this paper,the pretreatment and detection methods of food additives in fatty samples are reviewed.A rapid analysis method for the detection of additives in fatty food is established by using organic solvent water solution as aqueous two-phase extraction system combining with GC-MS technology.This thesis includes six sections.Part one:This section reviews the safety status of fatty food,the additive detection methods and sample pretreatment technology in fatty food,and the significance of this topic is explained.Part two:Based on isopropanol-NaCl-H₂O aqueous two-phase system,the antioxidants including the BHA（butylated hydroxyanisole）and the BHT（butylated hydroxytoluene）in biscuit samples are quickly determined by gas chromatograph coupled with mass spectrometry.The influence factors of the aqueous two phase system on extraction of BHA and BHT in biscuit samples are investigated detailedly.The results show that isopropanol has superbly abilities for extraction of BHA and BHT in biscuit samples.Sodium chloride gets high efficiency for salting out phase separation.In the procedures of biscuit samples pretreatment,the extraction rate of BHA and BHT is related to the volume fraction of isopropyl alcohol.When the volume ratio of water and isopropyl alcohol in aqueous two-phase system is approximately 3:2,the isopropyl alcohol and antioxidants in biscuits can fully contact,and the extraction rate is higher.Meanwhile,the amounts of liposoluble impurity in the extract of aqueous two-phase system and solvent extraction method are detected.The content of liposoluble impurity in the extract of isopropanol-NaCl-H₂O system is significantly lower than that of solvent extraction procedure.Therefore,the purification steps are greatly simplified.The C₁₈8 modified silica and primary secondary amine（PSA）are added in upper phase to eliminate the impurities.Then,the antioxidants in extract（upper phase）are directly analyzed by GC/MS.The proposed method has been applied to the determination of BHA and BHT in biscuit samples.The spiked recoveries are 85.7%⁹9.7%,and the detection limits are in the range of 2.6⁵.3 ng·g^-1.Part three:Tedinki hydroquinone（TBHQ）,butylated hydroxyanisole（BHA）and butylated hydroxytoluene（BHT）are three species of edible antioxidants that are often added to edible oil.In this experiment,the antioxidants are extracted efficiently by using acetonitrile-K₂HPO₄-H₂O system combined with gas chromatography-mass spectrometry（GC-MS）to detect.It is found that the extraction efficiency of TBHQ,BHA and BHT is higher when using acetonitrile aqueous solution.K₂HPO₄ is the best salting out phase salt in acetonitrile aqueous solution.The extraction rate of antioxidants（TBHQ,BHA and BHT）in edible oil is related to the volume fraction of acetonitrile aqueous solution.When the volume fraction of water and acetonitrile in aqueous two-phase system is about 50%,acetonitrile can fully contact with antioxidants（TBHQ,BHA and BHT）in edible oil,and the extraction rate is high.The content of fat soluble impurities in the extraction solution of double water phase extraction and non water soluble solvent extraction is compared.The results show that the content of fat soluble impurities in the aqueous two-phase system is lower.Adding C₁₈8 modified silica,primary secondary amine（PSA）and ester-bonded monolithic silica can effectively eliminate impurities,which simplifies the purification step.The method is used for the determination of antioxidants（TBHQ,BHA,BHT）in edible oil,the recovery rates are 87.1%⁹9.2%,and the detection limits are2.7⁵.9 ng·g^-1.Part four:Edible oil is usually stored in plastic containers such as plastic buckets and bottles which usually contain plasticizers.In this paper,9 kinds of phthalates in edible oil are extracted efficiently by acetonitrile-NaCl-H₂O aqueous two-phase system and be detected by gas chromatography-mass spectrometry（GC-MS）.Experiments explore the influence factors of the aqueous two phase system on extraction of phthalic acid esters.Through the discussion of experimental conditions including the selections of the organic solvent and phase separation salt,the volume fraction of water,the acetonitrile-NaCl-H₂O aqueous two-phase system is established to extract 9 kinds of phthalates from edible oil pretreatment,and the extraction rates are satisfactory.This method is used for the determination of 9 kinds of phthalate esters in edible oil.The recovery rates are78.5%¹02.3%,and the detection limits are 1.1⁶.2 ng·g^-1.Part five:During the study we mainly explore the pretreatment method of parabens antiseptic in food by aqueous two-phase system,using gas chromatography-mass spectrometry（GC/MS）determination.The experimental conditions of aqueous two-phase extraction are explored during the experiment,including the kinds of extractant,the type of salt,the volume fraction of water in the extractant,and the amount of PSA and C₁₈8 used to purify the agent.The experiments show that using anhydrous ethanol as extraction agent,sodium chloride as the separation effect of salt,ethanol and water volume ratio of4:1 are the best.When the dosage of PSA is 50 mg and the dosage of C₁₈8 is 50 mg,the impurities in the extract can be purified effectively.The method of extracting paraben preservatives in baking foods（MP,EP,PP,IPP,BP,IBP）for the determination of the recovery rates are 80.4%⁹6.4%with RSD value of 2.76%⁴.92%,the detection limits are3.8¹8.7 ng·g^-1.Part six:Determination of 6 kinds of parabens antiseptic in sausages is studied by aqueous two-phase extraction combined with gas chromatography-mass spectrometry.The experiment mainly explores the optimal extraction conditions of 6 kinds of parabens antiseptic aqueous two-phase extraction in sausages,including the selections of the extraction agent in aqueous two-phase,salt for salting out phase,extraction agent in the volume ratio of the extractant.And it involving the relationship between the use of PSA and C₁₈8 and the effect of purification of the upper phase extract.Considering the effects of these two factors,high extraction rate and good purifying,the experiment finally establishes the isopropanol-NaCl-H₂O aqueous two-phase system used for extracting 6kinds of parabens antiseptic in ham sausage.Gas chromatography-mass spectrometry（GC-MS）is used to determine the content of parabens antiseptic in different kinds of sausages.The average recovery rate is between 62.7%and 98.9%,and RSD are 1.64%³.79%.