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Urea-linked Covalent Organic Framework For Thin Film Microextraction Of Rhodamine B In Food Samples

Posted on:2023-02-26Degree:MasterType:Thesis
Country:ChinaCandidate:H L CaoFull Text:PDF
GTID:2531306818498824Subject:Food Science and Engineering
Abstract/Summary:PDF Full Text Request
Rhodamine B(RB)is an industrial dye with carcinogenicity and teratogenicity.Oral or skin contact with RB can lead to chronic or acute poisoning.Although RB is defined as prohibited food additive in many governments and regions,illegal application of RB in foodstuffs such as chili and pepper still exists because of its benefit in the promotion of the food sensory properties,threatening the health of our human.Consequently,development of rapid and sensitive methods for precise determination of trace RB is of great significance for food safety.Sample pretreatment is a key step in quantitative analysis of RB,which directly affects the accuracy and reproducibility of analytical results.Hence,this thesis aims to apply covalent organic framework(COF)with ordered structure and good stability as adsorbent for selective and rapid thin film microextraction of RB in food samples before high performance liquid chromatography-fluorescence detection(HPLC-FLD).The main results are as follows:(1)Three irreversible COFs were prepared for the adsorption of RB.The irreversible urea COF(COF-117)and two irreversible enamines COF(Tp Pa-1 and Tp BD)were prepared.The three COFs have good crystallinity and stability in four solvents(methanol,ethanol,acetonitrile and 0.1 mol L-1 HCl).The adsorption kinetic curves of COF-117,Tp Pa-1 and Tp BD for RB fit with the quasi-second-order model.The adsorption equilibrium time is 30 min.The adsorption of RB with different concentration fits well with the Langmuir model.The calculated maximum adsorption capacity of COF-117,Tp Pa-1 and Tp BD are 57.5,5.28 and 30.9 mg g-1,respectively.The abundant urea groups can interact with RB via electrostatic interaction,hydrogen bonding andπ-πinteraction,leading to better adsorption performance of COF-117 than Tp Pa-1 and Tp BD.The results show that COF-117 is a good adsorbent for RB.(2)A new quantitative method for RB based on COF-117 functionalized polytetrafluoroethylene membrane(COF-117-PTFE)was developed.COF-117 was covalently bonded to PTFE membrane via in situ growth strategy to prepare COF-117-PTFE.COF-117-PTFE was applied as adsorbent for thin film solid phase microextraction of RB.The developed thin film solid phase microextraction was coupled with HPLC-FLD for the determination of RB.The detection limit,quantitative limit and linear range were 0.007μg L-1,0.02μg L-1,0.1~100μg L-1,respectively.This method has good precision.Even in the presence of high concentration of citric acid,ascorbic acid,amaranth,capsanthin,methyl orange,methyl blue,SudanⅠand SudanⅢ,the extraction efficiency of RB remained stable.The recovery of RB in pepper and Sichuan peppercorn was 90.4%~102%,respectively,which proves the practicability of the developed method.
Keywords/Search Tags:rhodamine B, urea-linked covalent organic framework, covalent organic framework composite membrane, thin film solid phase microextraction
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