Construction Of Fluorescence Colorimetric Rapid Detection Method For Kaempferol And Folic Acid In Food

In recent years,improving food quality has become a key direction for the future development of food industry,and micronutrients in food are important indicators for food quality evaluation,but there is a lack of rapid detection methods suitable for vitamins and other micronutrients in food,and there is a lack of rapid detection technical means for food quality evaluation.In this paper,through the introduction of fluorescent materials and molecularly imprinted materials,a rapid detection method for kaempferol and folic acid in food is established,which can be applied to high-throughput detection and rapid analysis on site.（1）Fluorescent molecularly imprinted polymers（CDs@MIP）were prepared based on fluorescent materials—silanized carbon dots and molecular imprinting technology.On this basis,a high-throughput rapid detection technology for kaempferol was constructed using a polystyrene 96-well plate as a carrier.Silylated carbon dots were synthesized by a high temperature one-step method using anhydrous citric acid and silane coupler KH-602 as precursors.Then,CDs@MIP were prepared by sol-gel method.Silanized carbon dots were used as fluorescent material,kaempferol as target,3-aminopropyltriethoxysilane as functional monomer,ethyl orthosilicate as crosslinking agent,ammonia water as catalyst,hexadecyl trimethyl ammonium bromide as surfactant.The successfully prepared CDs@MIP was mixed and transferred to a 96-well microplate.After drying,the CDs@MIP microplate was obtained,and the fluorescence detection and analysis of kaempferol was carried out by a microplate reader.Under the optimal conditions,there was a good linear relationship in range of 0-25 mg·L^-1 between the fluorescence quenching intensity（F₀/F）of CDs@MIP microplate and the concentration of kaempferol,the detection limit is 15.05μg·L^-1.The constructed method was used in the detection of actual samples of vegetables,and the detection results showed good consistency with the detection results of high performance liquid chromatography.（2）A dual-emission ratio fluorescent probe was designed and synthesized and coupled with an application for smartphone sensing platform to achieve quantitative,visualization,and rapid analytical detection of folic acid.Firstly,water-soluble carbon dots were prepared by microwave-assisted method using citric acid and ethylenediamine as precursors.Under excitation at 360 nm,the optimized water-soluble carbon dots have an emission peak at 470nm,which is simply mixed with quantum dots with an emission peak at 585 nm to construct the dual-emission fluorescence ratiometric nanoprobes.With the increase of the amount of folic acid added,the fluorescence of the dual-emission fluorescence ratiometric nanoprobes was enhanced at 470 nm,and the fluorescence at 585 nm was quenched.The experimental results can be observed visually,realizing the visualization of rapid detection.Acquisition of fluorescence images in a UV dark box using a smartphone and using RGB models for analysis.In the linear range of 0-100 mg·L^-1,the fluorescence signals（G/R）of the dual-emission fluorescence ratiometric nanoprobes showed a good linear relationship with the concentration of folic acid,the detection limit is 22.13μg·L^-1.The dual-emission fluorescence ratiometric nanoprobes was used for the actual sample detection of milk powder,and consistent with the determination results of high performance liquid chromatography.