Investigations On Imprinting Materials For The Detection Of Estrogen And Aminoglycoside In Dairy Products

Dairy products play an important role in human daily diet.Estrogen and aminoglycoside antibiotics are two kinds of veterinary drug residues often detected in dairy products.Excessive use and abuse of estrogen and aminoglycosides in animals will lead to their residual accumulation in the animal body.If such animal derived food is ingested for a long time,it will cause serious damage to human body,such as reproductive dysfunction,brain nerve damage,hearing loss,liver and kidney damage.Therefore,it is of great significance to establish a detection method with high sensitivity and good stability.The complex matrix of dairy products,eliminating the serious interference of complex matrix,improving selectivity and sensitivity are the key to complex sample analysis.Therefore,it is necessary to develop a high-specific,fast and simple sample pretreatment technology.MIPs have the advantages of strong binding power,good thermal and chemical stability and high reusability.It can provide effective purification and selective adsorption.It can be used in sample pretreatment technology to separate and enrich the tested objects from complex sample matrix more efficiently,thus reducing matrix interference and improving the sensitivity and accuracy of the detection method.Two new molecularly imprinted polymers were prepared for the analysis and detection of the residues of two kinds of veterinary drugs in dairy products.The specific work is as follows:1.A new cross-linking functional monomer,2,5-divinylp-benzaldehyde(DVA),was prepared.The compound has the functions of both functional monomer and crosslinker.MIPs with high selectivity and affinity for estradiol and its analogues were prepared by using estradiol as template molecule and cross-linking functional monomer(DVA).The use of cross-linking functional monomer reduces the complex variables in the process of synthesis optimization and improves the preparation efficiency of MIPs.The morphology and structure of MIPs were characterized by Fourier transform infrared spectroscopy(FT-IR),Brunauer Emmett teller specific surface area analysis(BET),nuclear magnetic resonance(NMR)and scanning electron microscopy(SEM).The saturated adsorption capacity of the MIPs for estradiol was 46.2 mg g^-1,and the MIPs had excellent selective adsorption capacity for five estrogens(estrone,estradiol,estriol,estradiol benzoate and ethinylestradiol).The MIPs were used as solid phase microextraction(SPME)coating for sample pretreatment,and combined with ultra performance liquid chromatography-mass spectrometry(UPLC-MS/MS)for the determination of estrogen residues in dairy products.Under the optimal SPME experimental conditions,the MIPs-SPME-UPLC-MS/MS method was established for the sensitive detection of five estrogens in dairy products.The linear range of the five estrogens was0.5-10000 ng kg^-1 with good correlation coefficient(R²?0.9936).The limits of detection(LODs)and limits of quantitation(LOQs)were 0.08-0.26 ng kg^-1 and 0.26-0.87 ng kg^-1,respectively.The relative standard deviation(RSD)was less than 8.8%.The relative recoveries of five estrogens were 84.3%-105.0%,RSDs?7.8%.Three estrogens(estrone,estradiol and estriol)were detected in the milk samples without standard addition.The established method has wide linear range,low detection limit,high accuracy and good reproducibility.2.Using the DVA monomer prepared in the first part of the work,a vinyl functionalized covalent organic framework material(COFs-V)was synthesized with1,3,5-tris(4-aminophenyl)benzene.Then using tobramycin as the template and3-mercapto-2-butanone as the functional monomer,the click reaction was used to graft on the surface of the carrier COFs-V,and the imine-type molecularly imprinted covalent organic framework material was successfully prepared(CMIPs).Combining COFs with molecular imprinting technology can synthesize the excellent properties of these two types of materials and improve selectivity and adsorption capacity.The materials were characterized and analyzed by SEM,FT-IR,BET,X-ray powder diffraction(PXRD),X-ray photoelectron spectroscopy(XPS).The adsorption capacity of CMIPs to tobramycin was 15.8 mg g^-1,and CMIPs had excellent selectivity to tobramycin,kanamycin,amikacin,streptomycin,gentamicin and neomycin.It was used as the SPME coating for sample pretreatment.Under the best SPME experimental conditions,the CMIPs-SPME-UPLC-MS/MS method was established for the analysis and determination of aminoglycoside antibiotic residues in dairy samples.The results show that the six aminoglycoside antibiotics had good correlation coefficients in the linear range of 0.01-500?g kg^-1(R²?0.9910),and the LODs and LOQs were 0.002-0.015?g kg^-1 and 0.005-0.050?g kg^-1,respectively.The standard addition recovery rate was 86.2%-115.3%,RSDs?10.2%.The results show that the method combines excellent selectivity,sensitivity,accuracy and stability,and is suitable for the detection and analysis of trace aminoglycoside antibiotics in dairy products.