| In recent years,due to the drive of the economic interests,the lack of scientific knowledge and the loopholes of supervision system,there have been many food quality and safety issues,people are increasingly concerned about safety of food quality and dietary nutrition and other issues with these major food safety issues exposed.Now many of the chemical analysis methods have been studied by many researchers,many methods have become more mature,but many problems still cannot be broken,if you want to get more simple,fast,sensitive analysis method,we must develop new way.Fluorescence analysis is a more advanced chemical analysis method.There are most important features of the upconversion nanometer luminescent materials,it has chemical stability,non-toxic,no light flashing and light drift,and near-infrared excitation.Nowadays,the application of upconversion fluorescence analysis method to detect beneficial or harmful substances in food is rare,this paper is committed to the establishment of a food detection method with the integration of the upconversion fluorescence analysis method,develop a new,simple and sensitive food testing method.（1）A strategy for choline sensing based on in situ polymerization of aniline on the surface of upconverting nanoparticles: This paper synthesized a kind of up-conversion luminescent nanomaterials(Na YF4: Yb3+/Er3+)with Poly（acrylic acid）（PAA MW=1800）as a protective role.This paper observed a detection method of choline based on fluorescence of UCNPs quenched by polyaniline.The choline decomposes into H2O2 and betaine through the catalysis of choline oxidase at 37℃.The positive charges of aniline monomer under the environment of p H 3.0 interact with negative charges on the surface of UCNPs,and than the HRP and H2O2 make aniline monomers polymerize in-situ on the surface of the UCNPs to the polyanilineand the fluorescence quenching.According to the fluorescence spectrum diagram,content of H2O2 and choline in the samples can be analyzed.The detection concentration range of choline is 1-200μM,and the detection limit is 50 n M.The recovery of choline detection is between 97.7%-102.7% in the practical application of infant formula and eggs.This detection method can avoid the interference of other fluorescent substances.It is a selective,convenient,sensitive and simple detection method.（2）A detection method of the choline and hydrogenperoxide based on the near infrared luminescent nanomaterials: This paper synthesized a kind of upconversion luminescent nanomaterials(Na YF4:Yb3+/Tm3+)with Poly（acrylic acid）（PAA MW=1800）as a protective role.We found that the ferric iron ions have obvious quenching effect on up-conversion luminescent nanomaterials,and other common ions do not produce significant effect on its glow.In addition,H2O2 can oxidize bivalent iron ions into ferric iron ions(Fe3+)which make the conversion nanomaterials quench.Based on this,we developed a new method for the detection of hydrogen peroxide.Because the choline decomposes into H2O2 and betaine through the catalysis of choline oxidase at 37℃,and then H2O2 can oxidize bivalent iron ions（Fe2+）into ferric iron ions,ferric iron ions further make nanomaterials fluorescence quenching.Therefore,we developed a detection method of choline.According to the fluorescence spectrum diagram,content of H2O2 and choline in the samples can be analyzed.The detection concentration range of H2O2 is 0.25-5μM,and the detection limit is 0.1μM.The detection concentration range of choline is 1-60μM,and the detection limit is 0.5 μM.The recovery of choline detection is between95.0%-100.07% in the practical application of infant formula.This method using near-infrared light for testing has significance in biological analysis,it also can be used to test other organic material and reaction which produce the hydrogen peroxide in organisms.It is a selective,convenient,sensitive and simple detection method. |
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