| Melamine and its derivatives (ammeline (ANE), ammelide (ADE), and cyanuricacid (CYA)) are nontoxic by themselves, but if intaked by human, in case of strongacid or alkali solution, melamine will hydrolyse and form a harmful substances.Melamine tablewares and food packaging materials were prepared withmelamine-formaldehyde resin. When treated by light, heat, acid or repeated using,residues of MEL, ANE, ADE, CYA will migrate to the contacted food and cause thepollution to the food, which will be harmful to human. In this dissertation, weestablished several robust detection methods for melamine and its derivatives, andthen study the migration rule of of melamine from food contact materials to food, andcarried out the reasearch of risk assessment and process control of melaminetableware.In Chapter1, we reviewed the materials used in food contact materials and therelated analytical methods. Specially, the analytical methods in determination ofmelamine and its analogues in food contact products had been reviewed in detail. Theresearch background of the melamine contamination in food contact materials and therelated risk assessment, and industrial control were introduced. The research ideas,main contents, characteristics and innovations of this thesis had been pointed out.In the second chapter, including6parts, a series of methods for detection ofmelamine and its derivatives in food contact materials base on chromatography andelectrochemical analysis technology were established.(1) A HPLC method was developed for determination of melamine and cyanuricacid. Under the optimum conditions, linear responses were in the range of0.1–110mg/L and0.3–135mg/L, respectively. And the recoveries were in the range of101.7-102.2%and88.0-88.9%with the concentration of0.5mg/L melamine and cyanuricacid, R.S.D. were2.45–3.42%and3.54–4.10%, respectively. The LOD were0.02mg/L for melamine and0.08mg/L for cyanuric acid.(2) A novel HPLC method of determining monomer of melamine (MEL) and its derivatives including ammeline (ANE), ammelide (ADE) and cyanuric acid (CYA)was developed. Under the optimum conditions, the calibration curves were linearfrom0.5to10mg/L with LODs (S/N=3) of0.06mg/L,0.08mg/L,0.12mg/L and0.15mg/L for MEL, ANE, ADE and CYA, respectively. The method providedrecoveries of96.4–101.6%at the spiked concentration of1.0mg/kg, and RSD of thepeak height were between2.794.39%.(3) A liquid chromatography electrospray ionization tandem mass spectrometric(LC–ESI-MS/MS) method was developed to determine melamine migration fromfood contact materials and melamine tableware. The result indicated that thecalibration curves were linear over melamine concentration in the range o f3.00-130.00μg/L for different simulant solutions with LODs of1.00–3μg/L. The averagerecoveries at three spiked concentration levels of10.00,50.00and80.00μg/kg werein the range o f98%-104%with RSDs of3.05–3.65%.(4) HILIC-MS/MS was developed for simultaneously qualitative and quantitativedetermination of melamine and triazine-related by-products including ammelide,ammeline, and cyanuric acid in food contact materials. Linear responses wereobserved for samples ranging from0.1-20mg/L,1-200,0.5-100and1-200μg/Lfor melamine, ammelide, ammeline, and cyanuric acid, respectively. The methodprovided recoveries of83.4–126.2%at the spiked concentration of1μg/kg,10μg/kg,20μg/kg, and RSD of the peak height were between2.89-3.37%.(5) Melamine was found to have the ability of significant quenching of the ECLof CdS-K2S2O8system, based on which a highly sensitive approach for detection ofmelamine was proposed. Under the optimum conditions, the logarithmic plot of theinhibited ECL versus the concentration of melamine was linear over the range of1.0×10-9mol/L1.0×10-7mol/L. The corresponding LOD was8.0×10-10mol/L formelamine(S/N=3).(6) An electrochemiluminescent (ECL) method has been developed for thedetermination of melamine based on the inhibition of luminol ECL system. Thedecrease of ECL intensity was linearly proportional to the logarithm of melamineconcentration in the range of1100ng/mL with the detection limit of0.1ng/mL. Themethod has been successfully applied to determine melamine in dairy products andthe melamine tableware, and the recoveries were in the range98.5103.7%and95.5106.0%in dairy products and the melamine tableware, respectively. Some possibleco-existing species showed no interference in the determination of melamine. In the third chapter, a LC-MS/MS method had been applied to determine themelamine migration from food contact materials, and melamine monomer migrationrule and migration model had been established. Specially two parts had been studied.(1) The difference of melamine migration under different conditions such asdifferent types of food simulants, contact time and temperature, reuse times and thecondition of being heated by microwave had been studied in detail. The resultsshowed that melamine migration increases in acid foods and milk. In order to reducethe risk of melamine migration, the using temperature, bloom time, re-use frequencyand microwave heating power and time should be controlled when the melaminetableware is used.(2) A mathematical model (including diffusion coefficients and partitioncoefficients) for melamine migration from the food contact materials had beenestablised based on Fick law. The effect of soaking solution (4%acetic acid, waterand10%elthanol) and soaking time (40℃,70℃and90℃) were discussed. Theresults show that temperature has great influence on the diffusion coefficient andpartition coefficient. Diffusion coefficient of melamine increases with temperature,meanwhile the partition coefficient between the melamine tableware and simulantsolutions decreases. The diffusion coefficient of simulant solutions was in sequence of4%acetic acid> water>10%ethanol, the partition coefficient was in sequence of4%acetic acid <water <10%ethanol.In Chapter4, a security risk assessment about the foods for1-3years old childrenin the melamine tableware had been performed. The effect of types of food, aceticacid concentration, migration temperature, migration time and frequency of repeatedusing dan the microwave heating time and power on the rules of melamine migrationand the daily intake amount of melamine of1-3years old children had been discussed.And the results reached had been compared with data from the WHO TDI (0.2mg/Kg·bw), security risk assessment on the food intake of1-3year-old children up indifferent conditions of use melamine tableware had been performed and theappropriate recommendations had been put forward also.In Chapter5, the effect of different production process conditions on themigration of melamine in tableware melamine had been studied. The major processeswhich have great impact on melamine monomer residues were studied. In addition,we also examined the effects of the three factors (temperature, pressure and curing time) in "surface applique" and "pressure curing" process on melamine migrationfrom melamine tableware. Combined with the economic analysis, the orthogonal testresults showed that the optimal parameters of pressure and curing process was190/160℃for top/bottom temperature,150kg/cm2for pressure and60s for curingtime.
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