Detection Of Certain Harmful Substances In Milk Based On Solid-phase SERS Substrate

Foodborne diseases caused by food contamination are one of the most important problems affecting human health.Food contamination refers to the change process of food safety caused by poisonous and harmful substances in food.Therefore,the issue of food safety has always been paid more and more attention by people.The safety of food not only affects people's health,but in severe cases can lead to very serious diseases.Especially dairy products,as a necessity in the growth and development of children,once food safety problems arise,it will seriously affect the harmony and stability of the society.Milk is rich in many nutrients and nutrients are also very rich,which can promote the body's calcium absorption.However,the issue of milk safety has always been a concern for people.Milk is made into a variety of processed foods and is widely valued in the food market.However,food safety issues frequently occur,resulting in a serious decline in consumer confidence in milk foods.This thesis focuses on the detection of harmful substances in dairy products,and researches on the development of new detection technologies for antibiotic residues and melamine in milk,and establishes corresponding detection methods and actual sample application evaluation,in order to promote the supervision efficiency of the safety of dairy products market.Surface-enhanced Raman spectroscopy(SERS)is a new surface analysis technology that can study the structural information of material molecules at the molecular level.SERS has been widely used in analytical sciences,surface sciences,and biological sciences due to its high selectivity,high sensitivity,fingerprint information,non-destructive testing,and other characteristics,and has grown into a very powerful analysis tool.In this thesis,we have successfully developed several SERS substrates for the determination of harmful substances in dairy products.The specific research work is mainly divided into the following parts:(1)Silver nanoparticle-decorated TiO₂ nanotube array for solid-phase microextraction and SERS detection of?-Lactam antibiotic residue in milkWe have prepared silver-loaded titanium dioxide nanotube arrays(Ag/TNA)by anodic oxidation and UV reduction.Using Ag/TNA as the SERS substrate,solid-phase microextraction technology combined with SERS was used to detect?-Lactam antibiotic residues in milk,that is,?-Lactam antibiotic residues in milk were indirectly detected by detecting 2-mercapto-5-methyl-1,3,4-thiadiazole(C₃H₄N₂S₂,MMT),an enzymatic hydrolysate of antibiotics.Compared with the traditional classic silver sol substrate,Ag/TNA substrate is more sensitive to MMT,has the self-cleaning ability,and can be reusable.The results show that the linear range of the SERS sensor for MMT determination is 0.5-1000?mol/L,the linear correlation coefficient is 0.992,and the detection limit is 0.11?mol/L.The recovery rate is 91-110%through the analysis of milk samples.The standard deviation is 1.70-9.89%.(2)Self-assembled AgNPs substrate is used for SERS detection of melamine in milkWe used hydroxylamine hydrochloride as a reducing agent to prepare silver sol by chemical reduction,and then deposited silver nanoparticles on a clean glass plate.Using self-assembled AgNPs as the SERS substrate,we constructed a SERS detection method for melamine in dairy products.In the experiment,the p H value of the solution and the wavelength of excitation laser are optimized.This method is applied to the analysis of actual milk samples,the recovery rate of the addition is 92-126%,and the relative standard deviation is about 10%under 532 nm excitation laser,the adding standard recovery is 98-130%,and the relative standard deviation is also about 10% under 633 nm excitation laser.