The Preparation Of A Nolve Cu(Ⅱ) Chromogenic Sensor And Its Application In Food

With the development of human society,heavy metal ion pollution has become an important factor that seriously threatens human health.Ingestion from food is one of the main sources of human weight metal,so the detection of heavy metal ions in food is particularly important.However,the current heavy metal ion detection methods,whether they are traditional large-scale instrumentation methods or various rapid detection methods,cannot meet the requirements of low cost and high accuracy at the same time.This is precisely the difficulty of research on food heavy metal ion detection methods and the comprehensive detection requirements.Pain points covered by the market.In order to solve the above problems,this paper uses polyacrylonitrile fiber(PAN)as the matrix material and based on the mechanism of chelation and adsorption of heavy metal ions,a series of Cu(Ⅱ)chromogenic fibers with enrichment,separation,and detection functions are prepared.Based on this,a Cu(Ⅱ)chromogenic sensor was constructed and applied to the detection of Cu(Ⅱ)in food,with satisfactory results.The paper adopted PAN reacts with four organic compound ligands under microwave-assisted heating conditions to prepare chelated fibers,and then uses this method to graft the developer to obtain chromogenic fibers(PAN-MP-PAR,PAN-DETA-PAR,PAN-HAM-PAR,PAN-MB-PAR),which is the key chromogenic material for chromogenic sensors.Based on the previous single-factor experiments,the reasonable experimental ranges of parameters such as reaction time,temperature,and molar ratio of raw materials were roughly determined.The key parameters of the synthesis process were optimized by the response surface method for its adsorption of Cu(Ⅱ).The amount is a measurement index,which is comprehensively determined in combination with the color change before and after the fiber synthesis reaction.Among them,the best reaction conditions for the first step chelation reaction are PAN-MP at 130 ℃,15 min,MP: PAN=2: 1;PAN-DETA is 125 ℃,10 min,DETA: PAN=2: 1;PAN-HAM It is 140 ℃,35 min,HAM: PAN=3: 1;PAN-MB is 140 ℃,35 min,MB: PAN=3: 1.In the second step,the conditions for grafting PAR were 120 ℃,15 min,and PAR: PAN was 1: 1.The characteristics of the structure and morphology of the chromogenic fiber before and after synthesis were characterized by FT-TR,SEM,XRD and XPS to confirm the above key-forming mechanism.This thesis is a systematic study the adsorption performance of the chromogenic fiber on heavy metal ions,the types of heavy metal ions,the p H value of the buffer solution,the reaction temperature,and the reaction time.The results show that the four kinds of chromogenic fibers have good adsorption selectivity for Cu(Ⅱ),and the optimal adsorption p H is around 6.The experimental measurement shows that when adsorbed at 308 K for 6 h,the adsorption amount of PAN-MP-PAR is 188 mg/g,PAN-DETA-PAR is 161 mg/g,PAN-HAM-PAR is 142 mg/g,and PAN-MB-PAR is 135 mg/g.The study of the reaction mechanism of Cu(Ⅱ)adsorption by chromogenic fibers found that the adsorption isotherms of the four chromogenic fibers fit well with the Langmuir model.It is close to the experimental value.The fitting results of the kinetic model show that the quasi-second-order kinetic equation is more suitable for describing the adsorption process of the four colored fibers,which means that the adsorption process is chemisorption,and the reaction rate is determined by the concentration of Cu(Ⅱ)and the chromogenic fibers The chemical reaction process between the active reaction sites in the medium is determined,not the transport process of Cu(Ⅱ).The results of adsorption thermodynamics show that the ΔG is negative,ΔS and ΔH are positive,which means this reaction is spontaneously,endothermic and chaotic.The thesis has also prepared a chromogenic sensor using chromogenic fibers as the key chromogenic material,and the qualitative detection method of Cu(Ⅱ)was constructed.The chromogenic properties of four chromogenic fibers and the effects of the p H value of the buffer solution,the types of heavy metal ions,the reaction time,and the initial concentration of Cu(Ⅱ)were studied using a chromogenic sensor.The results show that under the guidance of the design model of this paper,a chromogenic sensor can be prepared at a lower cost.Based on the photos obtained by the image acquisition system,it can be found that when p H is 6,the chromogenic reaction is more favorable;The selectivity of Cu(Ⅱ)helps the chromogenic sensor to realize the qualitative detection of Cu(Ⅱ);as the reaction time between the chromogenic fiber and Cu(Ⅱ)increases,the fiber color gradually deepens;the initial concentration of Cu(Ⅱ)increases,and the chromogenic reaction phenomenon The more obvious,when the initial concentration of Cu(Ⅱ)is higher than 200 mg/L,it is difficult for the naked eye to distinguish the color change.This paper characterized the fibers before and after the chromogenic fiber reacted with Cu(Ⅱ)in the chromogenic sensor by FT-IR,SEM,EDS,etc.,and the chromogenic mechanism of Cu(Ⅱ)by the chromogenic fibers in the chromogenic sensor the study.The XPS test results of PAN-MP-PAR show that Cu(Ⅱ)forms a flat tetragonal chelate structure with N and O in the chromogenic fiber,and UV-vis indicates that the light absorption cutoff edges before and after the color-developing reaction of the fiber are at 689 nm and 763 nm,the red shift caused the HOMO-LUMO energy level difference to decrease from 1.70 e V to 1.54 e V.This Cu(Ⅱ)adsorption caused the electrons in the colored fibers to rearrange in the system.In order to further realize the quantitative detection of Cu(Ⅱ),the sixth chapter construct a standard Cu(Ⅱ)chromogenic panel using PAN-DETA-PAR,and complete set of Cu(Ⅱ)including a food sample pretreatment method was developed Cu(Ⅱ)quantitative detection method,the quantitative concentration range is 0～200 mg / L,which verifies the feasibility of the method from multiple angles.The content of Cu(Ⅱ)in eggplant,spinach,white radish,Chinese cabbage,and shiitake mushroom was determined by the Cu(Ⅱ)chromogenic sensor method.The results were similar to the ICP-AES method and the results were satisfactory.