Electrochemical Detection Of Aromatic Amines In Food Contact Materials

4,4’-Diaminodiphenylmethane（DDM）is a typical primary aromatic amine in food-contact materials.,As one of the decomposition products of ammonia ester binders and azo fuel,DDM is often used as an additive in nylon products to enhance heat resistance.There are food-contact rules and laws to standardise the usage of DDM both in foreign and demotic countries because DDM is one of the arcing,enic highly toxic substances in level 2A.In recent years,withincreaseasing of ports from China,the method to detect aromatic amines in food-contact materials is really in need.However,the existing detection methods are time-consuming,costly and complicated due to the high diligence of large instruments such as chromatography and mass spectrometry.Thus,building a rapid and accurate system to detect aromatic amines is meaningful.Electrochemical analysis has the advantages of fast response,portable equipment and simple operation.Molecularly Imprinted Polymer has the function of specific identification.In this thesis,the author prepared two molecularly imprinted electrochemical sensors for 4,4’-diaminodiphenylmethane to detect 4,4’-diaminodiphenylmethane with the help of electrochemical analysis and Molecularly Imprinted Polymer.The research procedures and main conclusions include:Direct electrochemical detection of 4,4’-diaminodiphenylmethane was carried out using a three-electrode system to investigate the current response of 4,4’-diaminodiphenylmethane at different electrodes and further investigate the oxidation characteristics of 4,4’-diaminodiphenylmethane under other conditions,and to increase the currrecereactionby adding cetyltrimethylammonium bromide（CTAB）was added to increase the current response.The results showed that the gold and platinum electrodes could not be used for electrochemical testing due to passivation;e glassy carbon electrode（GCE）showed a linear relationship between the current response and the target concentration under acidic conditions,a detection limit of 3.1 umol/L.CTAB multiplied the present reaction under alkaline conditions,and the detection limit was reduced to 0.046 umol/L after optimisation of the test conditions.The recoveries were above 94%.Molecularly imprinted molecular films（MIP）were prepared by electrodeposition on the surface of glassy carbon electrodes（GCE）using carboxylated carbon nanotubes（OH-SWCNT）as sensitising materials and DDM and pyrrole（PPY）as template molecules,and single-factor experiments optimised functional monomers,respectively,and the preparation process.The surface morphology and detection capability of the imprinted electrodes were characterised by scanning electron microscopy（SEM）and electrochemical analysis.The imprinted films were rough and porous with electrochemical inertness,and OH-SWCNT increased the current response.The following conditions were determined to prepare the DDM molecularly imprinted sensor:carboxylated carbon nanotube modification concentration of 2.5mg/L,time pyrrole to DDM ratio 5:six,6 cycles of voltammetric scanning,15 min elution and 12 min incubation time.The electrodeposited DDM electrochemical sensor exhibited excellent detection performance and reproducibility with a linear range of 10-50 umol/L and a detection limit of 116 ng/L.The magnetic molecularly imprinted polymer（MMIP）was prepared by a sol-gel method using magnetic Fe₃O₄ as the core and single-walled carbon nanotubes as the sensitising material.The MMIP was combined with a magnetically-controlled glassy carbon electrode to construct a MIP sensor to enrich DDM using superparamagnetic iron nano-ions and DDM-imprinted pores.The sensor was characterised by electrocharacteriseddance spectroscopy（EIS）and cyclic voltammetry（CV）.The magnetically-controlled MIP sensor showed good reproducibility concerning DDM adsorption.Therption-detachment of MMIP enabled the sensor to be automatically renewed,and the detection limit was reduced to 0.015nmol/L after optioptimisationthe preparation process using differential pulse voltammetry.