The Preparation Of Molecularly Imprinted Microcolumn And Their Application In Microextraction Of Vanilla-flavor Spice

Vanilla-flavor enhancers?VFEs?are very common food additives.This kind of spice can produce pleasant smell,and are often used in daily chemical,food,tobacco,soap and as a chemical intermediate in the production of pharmaceutical.Because of the high cost of natural flavor,most of the VFEs are obtained through chemical synthesis.It has been deemed that these synthetic food additives can have side effects on liver and kidney functions of the body which can trigger migraine headaches,nausea and vomiting.Infant physical growth is not complete,they have little resistance to harmful substances and their health are more easily influenced.Therefore,the amount of vanilla-flavor enhancers in infant milk powder should be detected in order to ensure the safety of little baby.In this paper,the molecularly imprinted monolithic column material was synthesized and applied to the selective extraction and detection of vanillin and methyl vanillin in infant milk powder.Molecularly imprinted polymer microcolumn?MIPM?combined with specific selectivity of molecular imprinting polymer and simple preparation,many different sizes of macro voids and flow-through channels of the material,which makes it easy to sensitively detect the trace analytes in complex samples.By in situ polymerization method,a novel molecularly imprinted polymer micro column was synthesized in a micro pipette tip,and the reaction conditions was optimized.The stability,physical morphology structure and the selectivity of the material was characterized by different instruments.The material was used to solid phase microextraction for determination of the vanillin?VN?and methyl vanillin?MV?in milk powder.A high sensitivity of trace component in high selectivity quantitative detection method had been developed coupling with HPLC,the method is simple,rapid,high sensitivity and selectivity.The main contents of this paper include the following three parts:?1?In this paper,vanillin was used as template,and the hybrid molecularly imprinted polymer microcolumn was prepared in a micro pipette tip by sol-gel method.The reaction conditions,such as the ratio and volume of inorganic solution to organic solution,the amount of initiator were optimized in the prepared process.And the material was characterized by thermogravimetric analysis?TGA?,scanning electron microscopy?SEM?and Fourier transform infrared spectroscopy?FT-IR?method,those detective method indicated that the material has well physicochemical property,such as good fluid permeability and thermal stability.The hybrid molecularly imprinted microcolumn material was applied to the SPME of vanillin and methyl vanillin in milk powder samples.The SPME conditions,such as the type,flow rate and volume of eluent,the volume,flow rate,pH and ionic strength of sample solution were optimized.A sensitive and accurate analysis method was established to quantitatively detect vanillin and methyl vanillin of milk powder sample.The experimental results show that the concentration scope of good linear relationship for VN and MV are all in 10-3000?g·kg^-1,with R² 0.9999 for VN and 0.9996 for MV.LODs?S/N=3?are 3,5?g·kg^-1,respectively.The recovery are 88.3-93.9%for VN and 89.0-96.9%for MV,respectively.The method was applied to actual milk powder samples measurement of vanillin and methyl vanillin,and the result is satisfied.?2?To prevent template leakaging,improve detection sensitivity,nonylphenol?NP?was used as the template.Through optimizing the synthetic conditions,a pseudo template hybrid molecularly imprinted polymer microcolumn was synthesized by sol-gel method in order to detect VN and MV.The stability of the material was proved by thermogravimetric analysis method,and the physical morphology structure and selectivity of the material were characterized by scanning electron microscopy?SEM?and Fourier transform infrared spectroscopy?FT-IR?method,respectively.The prepared pseudo template hybrid molecularly imprinted polymer microcolumn in optimal synthetic conditions were used to solid phase microextraction for MV and VN of milk powder,and a rapid,sensitive and efficient method for the quantitative analysis was established.The concentration scope of good linear relationship for VN and MV are all in 1-3000?g·kg^-1.The detection limits?S/N=3?are 0.5,1?g·kg^-1,the recovery are 92.2-101.0%for VN and 91.5-98.7%for MV,respectively.The method showed that after using the dummy imprinting technique,which was developed by using structural analogue as pseudo-template,can avoid the leakage of the template,a higher sensitivity was gotten for the method.?3?In this work,template molecule,cross-linker,monomer and initiator were nonyl phenol,ethylene glycol dimethacrylate,methacrylic acid,azobisisobutyronitrile,respectively.A molecular imprinting polymer microcolumn was prepared in methanol solution by in situ polymerization.In order to get good permeability and high recognition capacity of the MIM,functional monomer,porogen and the amount of initiator were optimized in the synthetic process.The stability,morphology structure and the selectivity of the material were characterized by thermogravimetric analysis?TGA?,scanning electron microscope?SEM?and Fourier transform infrared spectroscopy?FT-IR?method,respectively.The imprinted factors of VN and MV were 3.56 and 2.04 for imprinted column,respectively,which indicated that the imprinted column had good selectivity for vanillin and methyl vanillin.The material were used in solid phase microextraction to determination of VN and MV in infant milk powder combined with HPLC and the extraction conditions were optimized.A rapid and efficient method for the quantitative and qualitative analysis was established.We found that good linear relationship were gotten in the concentration scope of 2-3000?g·kg^-1 for VN and 3-2000?g·kg^-1 for MV,and R² is 0.9947 for VN and 0.9978 for MV.The detection limits?S/N=3?are 0.6,1?g·kg^-1,and the recovery are 83.0-110.2%and 80.6-101.1%,respectively.Compared the organic column material with the hybrid column material,as the results showed,organic column and hybrid column has the similar detective sensitivity,but the hybrid column material has better physical morphology structure and mechanical strength.