| Bisphenol A(BPA)is an organic chemical material for producing polycarbonate,epoxy resin and other plastic products,and it is a typical endocrine disruptor,which can cause insufficient or excessive secretion of normal estrogen.As the main substitute for BPA,bisphenol S(BPS)also retains the similar estrogenic activity of BPA,which will harm the human body and the ecological environment.The content of BPA and BPS in food is low,the pollution mainly comes from the contact between food and packagings containing BPA and BPS during the processing and packaging.Therefore,it is of great significance to find a high-efficiency adsorbent to establish a method for enrichment and determination of BPA and BPS in food packagings.Covalent organic frameworks(COFs)are a kind of two-dimensional or three-dimensional porous crystalline structure with abundant ??conjugated groups,large specific surface area,stable physical and chemical properties,which can conjugate with aromatic compounds to achieve enrichment.In this paper,a ?-ketoenamine-linked COF DQTP synthesized by 2,6-diaminoanthraquinone(DQ)and 1,3,5-triformylphloroglucinol(TP)was selected as absorbent.DQTP was modified on the stainless steel wire and graphite pencil to respectively establish an electro-enhanced solid-phase microextraction(EE-SPME)combined with gas chromatography-flame ionization detector(GC-FID)method and an electrochemical sensor for enrichment and determination of BPA and BPS in food packagings.The main studies and results are as follows:(1)DQTP was in situ bonded to the stainless steel wire via facile solution-phase approach and combined with an external electric field to construct an EE-SPME device to preconcentrate BPA in food packagings.The fiber prepared by this method had higher extraction efficiency compared with different SPME fibers.The shift of C=C in DQTP and the bathochromic shift of the characteristic peak for BPA before and after adsorption,as well as Chemdraw structure simulation,preliminarily assumed that the adsorption process between DQTP and BPA is primarily controlled by ?-? interaction,porosity effect and hydrogen bonding effect.Combined with GC-FID for enrichment and determination of BPA in food packagings,the linear range of this established method was 0.05?10 ?g/mL,and the detection limit was 0.003 ?g/mL(S/N=3).The extraction equilibrium could be reached within 10 min with good precision and reproducibility.This method had been successfully applied to the determination of BPA in food packagings(mineral water bottles,milk boxes,and milk tea cups).(2)An electrochemical sensor based on DQTP modified pencil graphite electrode(PGE)was developed for the simultaneous determination of BPA and BPS in food packagings.The?-ketoenamine-linked COF DQTP was synthesized by solvothermal method.DQTP suspension was drop-casted on PGE,and assembled with a 3D-printed electrode clamp to prepare a DQTP/PGE sensor.The periodic ?-arrays and suitable pore size of DQTP facilitated the accumulation of BPA and BPS via ?-? conjugate aggregation and porosity effect,and then the accumulated BPA and BPS could be detected by differential pulse voltammetry.The linear range of this method was 0.5?30 ?mol/L for two bisphenols,and the detection limit was 0.15?mol/L(S/N=3).The method was successfully applied to the simultaneous determination of BPA and BPS in food packagings(polycarbonate bottles,mineral water bottles,plastic boxes,and hermetic bags)which were in good agreement with those of HPLC method,and the quantitative analysis of BPA and BPS migration in plastic beverage bottles.In summary,two analytical methods developed by ?-ketenamine linked COF DQTP can achieve rapid enrichment and determination of bisphenols in food packagings,providing a new method for the determination of bisphenols in complex samples,as well as a new application for COFs in the field of sample pretreatment and electrochemical sensing. |
PDF Full Text Request