Preparation Of Monolithic Column With Molecularly Imprinted Polymers And Its Application For Separation And Analysis Of Chemical Risk Factors

In the process of production and processing of food contact materials（FCMs）,some monomers and production additives were retained,such as aromatic amines,phenolic compounds and plasticizers.These chemical risk factors may migrate into food,causing food safety issues,and have toxic effects on the human body by contacting with skin,mucous membranes or direct ingestion.So,the detection technology of these chemical risk factors must be developed to monitor the quality of FCMs.The matrix of FCMs samples is often complex,and the chemical risk factors is at a low level and the migration quantity is also lower.Therefore,it is of great significance for food safety and human health to develop highly selective separation and sensitive detection methods for chemical risk factors in FCMs.Solid phase microextraction（SPME）has been widely applied in the field of separation and analysis in recent years.The selectivity and extraction efficiency of SPME was affected by the adsorbent materials used.Molecularly imprinted polymers（MIPs）are a class of materials with specific recognition,which have three-dimensional cavities and imprinting sites with complementarities for template molecules.MIPs can be used as adsorption materials for SPME to improve its extraction selectivity.Most MIPs are prepared with a single functional monomer,which has relatively weak interaction with the template molecules and limits the molecular recognition ability.The molecularly imprinted strategy with bifunctional monomer is expected to improve the specific recognition performance of MIPs for the template molecule and their structural analogues.In this work,two types of MIPs monolithic column were synthesized and used as adsorption materials of SPME to combine with HPLC.They were applied to the separation and detection of aromatic amines and phenolic compounds in FCMs.Two new methods were established for the efficient separation and analysis of aromatic amines and phenolic compounds in complex matrix.The main contents are as follows:（1）A BNZ-MIP monolithic column was prepared by in situ polymerization in the pipette tip,which using benzidine（BNZ）as template molecule and 4-vinylpyridine（4-VP）as functional monomer.The BNZ-MIP monolithic column was used as the extraction material for SPME to combine with HPLC for simultaneous determination of six aromatic amines includingbenzidine,4,4′-methylenedianiline,3,3′-Dimethoxybenzidine,2-methoxy-5-methylaniline,3,3′-dimethyl-4,4′-diaminodiphenylmethaneand4-aminobiphenyl.The BNZ-MIP monolithic column was characterized by Fourier transform infrared spectroscopy,scanning electron microscopy,thermogravimetric analysis,nitrogen adsorption and desorption experiments.The results showed that BNZ-MIP monolithic column has large surface area and continuous pore structure,which is conductive to the adsorption of analyte.The results of adsorption experiments showed that the BNZ-MIP monolithic column had good adsorption selectivity for the six aromatic amines.The optimal SPME conditions were as follows:sample solution volume（2.0 m L）,sample solution flow rate(0.2 m L min^-1),salt concentration（20%w/v）,eluent（methanol）,eluent volume（400μL）and eluent flow rate(0.05 m L min^-1).Under the optimum extraction conditions,the separation and analysis method for six aromatic amines in FCMs were established,which had a wide linear range(0.6-500μg kg^-1),low detection limit(0.2-1.5μg kg^-1),good reproducibility（3.9-8.6%）and satisfactory recoveries（81.7-110.9%）.The method was applied for the determination of aromatic amines migration in six types of polyamide kitchenware samples.（2）An acrylyl group modifiedβ-cyclodextrin（A-β-CD）was synthesized,and an A-β-CD/4-VP-MIP monolithic column was prepared in the pipette tip by in situ polymerization,which used phenol and bisphenol A as dual template molecules,A-β-CD and4-VP as bifunctional monomer.The A-β-CD/4-VP-MIP monolithic column was used as extraction material for SPME to combine with HPLC for simultaneous detection of eight phenolics:phenol,m-cresol,p-tert-butylphenol,bisphenol A,bisphenol B,bisphenol E,bisphenol AP and bisphenol Z.The A-β-CD/4-VP-MIP monolithic column was characterized by Fourier transform infrared spectroscopy,scanning electron microscopy,thermogravimetric analysis,nitrogen adsorption and desorption experiments.The results showed that the A-β-CD/4-VP-MIP is loose and porous with large specific surface area and continuous pore structure,which is conducive to the adsorption of analyte.The adsorption experiment showed that the A-β-CD/4-VP-MIP monolithic column has good molecular recognition performance and adsorption selectivity for the eight phenolics.The optimized SPME conditions were as follows:sample solvent（water）,sample solution volume（4.0 m L）,sample solution flow rate(0.2 m L min^-1),sample solution p H（5.0）,salt concentration（0%w/v）,eluent（methanol）,eluent volume（200μL）and eluent flow rate(0.05 m L min^-1).A new separation and analysis method of eight phenolic compounds was established,and the linear range of the method（LRs）was 0.5-200μg L^-1（R²>0.997）,the limit of detection（LODs,S/N=3）was 0.15-0.67μg L^-1,the intra-day and intra-day relative standard deviations（RSDs）was lower than7.0%and the recoveries were 83.3-111.5%,indicating that the method had high sensitivity and good reproducibility.The method was applied for the determination of migration amount of eight phenolic compounds in five polycarbonate cup samples with satisfactory results.