Study On Recognition Of Sulfonamides Based On Surface Enhanced Raman Spectroscopy And Molecular Imprinting Technique

Sulfonamides（SAs）are a group of antimicrobials,mainly used for prevention and treatment of infectious diseases,and also used as feed additives.Many countries have strengthened the regulation of SAs residues due to its teratogenic and carcinogenic properties.However,it is a challenge to achieve sensitive detection of SAs due to they are together with different inpurities at trace levels.The current methods for detecting SAs mainly include liquid chromatography and mass spectrometry,but the methods are time-consuming and complicated,and cannot provide on-site feedback.Therefore,it is an urgent to develop a rapid and effective method for detection of SAs from the environment.Surface enhanced Raman spectroscopy（SERS）has emerged as a promising spectroscopic technique due to its unique advantages of“spectroscopic fingerprint”,fast response.Nevertheless,the applications of SERS are limited for their lack of selectivity and susceptibility to interference.In order to promote the application of SERS technology in the detection of small molecules such as antibiotics,this thesis aims to combine molecular imprinting technique with SERS.SERS substrate of silver-molecularly imprinted polymer was prepared and a fast and effective method for the detection of SAs was established.The main results are as follows:1.SERS substrates based on silver-molecularly imprinted polymer were prepared by two methods.The core-shell silver-molecularly imprinted polymer SERS substrate（Ag@MIP）was prepared by surface imprinting method,while the silver microspheres with rough surface were prepared by optimizing the synthesis time and the added amount of citric acid during the synthesis process.In addition,silver-doped molecularly imprinted polymer（MIP@Ag NPs）SERS substrate was prepared by in-situ method.The amount of crosslinker,initiator addition and silver nitrate addition were optimized.Comparison of the adsorption properties of silver-molecularly imprinted polymers synthesized by the two methods,Ag@MIP reached adsorption equilibrium at 30 min with an adsorption capacity of 2.65 mg/g,and MIP@Ag NPs reached adsorption equilibrium at 70 min with an adsorption capacity of 6.08 mg/g.2.The MIP@Ag NPs SERS substrate was prepared by the in-situ method,and then the rapid detection method for sulfamethazine was established.The linear range for sulfamethazine quantitative detection was in the range of 10^-10 mol/L to 10^-6 mol/L.The corresponding regression equations were expressed as:y=26063.4-2391.6x（R²=0.9955）,while the limit of detection was 10^-10 mol/L.The MIP@Ag NPs SERS substrate exhibited good reproducibility,excellent SERS performance after 14 days of storage at room temperature,and could be reused with three times.The recovery rates of practical water samples and milk samples were85.1%～102.5%and 85.2%～98.0%,respectively.The limit of detection can meet the EU EMEA/MRL/026/95 quantitative standard of 100μg/kg.3.Based on the recognition mechanism of molecularly imprinted polymers,the detection method with screening-like ability for a variety of SAs was established by changing the template molecule to regulate the size of the molecularly imprinted hole,and its mechanism was analyzed.Sulfanilamide,sulfathiazole and sulfamethazine were selected as template molecules and established calibration curves,respectively.Seven kinds of SAs were detected for single-component residues and multi-component residues.When sulfathiazole was used as the template molecule,the substrate exhibited the best detection performance.The detection accuracy can meet the maximum residue limit of SAs in milk of European Union and China.