Study On Detection Method Of Harmful Substances In Milk Based On Fluorescence Spectrum

Milk is rich in a variety of nutrients needed by the human body.It is a kind of popular common food.In order to supervise and improve the quality of milk and ensure its food safety,it is necessary to develop fast,sensitive and accurate detection technology to detect harmful substances that may exist in milk.However,milk is a complex mixture.The technology of milk detection faces many challenges.On the basis of studying the spectral characteristics of milk and its monomers,a method for the determination of antibiotic residues and non-protein nitrogen adulterants in milk is established based on fluorescence spectroscopy.Under the excitation of light,milk has strong scattering and complex fluorescence.In addition,many of the harmful substances to be detected are weak fluorescent substances or non fluorescent substances,which cannot be detected by conventional fluorescence spectroscopy.Therefore,spectral data are measured and analyzed,models and algorithms are established,and fluorescent probes with excellent performance are developed.Sensitive and accurate detection of two kinds of common harmful substances is realized.The details are as follows:1.Study on the fluorescence spectrum characteristics of milk and its main monomers.Three dimensional fluorescence spectra of ninety-three milk samples that basically cover all varieties sold on the market are measured.The fluorescence spectra of milk and its main monomers are analyzed in detail.The fluorescence spectral characteristics of milk are obtained.It is confirmed that tryptophan in casein is the main fluorescence substance of milk;Based on the fingerprint of three-dimensional fluorescence spectrum,the characteristic parameters of fluorescence spectrum are extracted.The fingerprint database of milk is established;The density functional theory is applied to establish the ground state and excited state models.The generation mechanism of milk fluorescence is analyzed.It lays a foundation for the development of detection methods for harmful substances in milk.2.The detection method of antibiotic residues in milk based on fluorescence spectrum is established.On the basis of studying the absorption spectrum and fluorescence spectrum characteristics of six kinds of common antibiotics,the corresponding accurate detection methods for antibiotics in milk are established according to three types of antibiotics: strong fluorescence,fluorescence spectrum overlapping with milk fluorescence and weak(no)fluorescence.Firstly,taking ofloxacin,a strong fluorescent antibiotic with rigid structure and conjugated double bonds,as an example,a direct quantitative detection method based on its fluorescence spectrum is established.Its universality is verified;Secondly,taking sulfamethoxazole as an example,which has strong fluorescence but greatly overlaps with the fluorescence of milk and cannot be directly detected.The fluorescence spectrum and multivariate statistical analysis geometry are used to model and calculate the spectral data.Quantitative detection method is established;Third,taking the weak fluorescent antibiotic tetracycline as an example,a deep ultraviolet fluorescence emission carbon dots is developed as a fluorescence probe to establish a method for the detection of weak(non)fluorescent antibiotics in milk.The detection limit of the established method reaches or is lower than the limit value of the national standard.3.The detection method of non-protein nitrogen adulterants in milk based on fluorescence spectrum is established.Melamine,urea and dicyandiamide are three common non-protein nitrogen adulterated harmful substances,whose fluorescence signal is weak and difficult to detect.Therefore,combined with nanotechnology,the corresponding fluorescence probe is developed.Based on the interaction between molecules and their groups,the sensitive on and off of fluorescence signals are used to realize the sensitive and accurate detection of non-protein nitrogen adulterants in milk.Firstly,the principle that melamine and gold nanoparticles can effectively combine and the fluorescence of sodium fluorescein can be quenched by gold nanoparticles is established.A method based on sodium fluorescein and gold nanoparticles is established to detect melamine in milk;Secondly,a p H sensitive carbon dots is developed as a fluorescence probe.Based on the principle that urease hydrolyzes urea to increase p H,and the fluorescence of the carbon dots will be quenched with the increase of p H,a method for detecting urea in milk is established based on p H sensitive carbon dots and urease;Third,α-naphthol diacetyl dicyandiamide system is constructed.Based on the principle that the reaction product of dicyandiamide with α-naphthol and diacetyl will quench the fluorescence of α-naphthol due to the internal filtering effect.A method for the determination of dicyandiamide in milk is established.The detection limit of the established method is lower than the limit value of the national standard.4.Establishment and application of transient fluorescence spectrum detection system.In order to quickly and accurately identify the types of dairy products and the harmful substances in milk,a set of transient fluorescence spectrum detection system is built.The system is used to measure the time-resolved fluorescence spectra of different kinds of dairy products.Combined with the principal component analysis model to process the spectral data,a method for identifying different kinds of dairy products is established.The rapid differentiation of dairy products is realized;The system is used to measure the time-resolved fluorescence spectrum of milk containing ofloxacin and levofloxacin.Based on fluorescence lifetime analysis,a qualitative detection method for antibiotic residues in milk is established.Rapid identification of antibiotic residues in milk is realized.The research work in this paper expands the fluorescence spectrum analysis and detection technology of complex mixtures.A new method is developed for the detection of milk.It can provide support for effective monitoring of milk food safety.