Detection Of Bisphenol A Residues In Food Contact Materials

Bisphenol A can be used as a lining material for industrial plastics and food cans to improve the performance of packaging materials.However,bisphenol A has endocrine disrupting effects on human body,which seriously affects human health.Therefore,it is important to establish a sensitive and simple method for bisphenol A determination.Electrochemical sensors are preferred for their good reliability,fast response time,inexpensive instrumentation,low cost,simple operation,high sensitivity,good selectivity and miniaturization as well as the possibility of in situ analysis.Metal organic backbones（MOFs）have important advantages for the electrochemical adsorption of bisphenol A due to their large specific surface area,abundant active sites and controllable structure.In order to solve the problem of highly sensitive detection of bisphenol A residues in food contact materials,it is necessary to address the conductivity of MOFs materials in electrochemical detection.In this work,four new MOFs materials were improved and developed as electrochemical sensors and applied to the detection of bisphenol A in food contact materials.The main research contents and results are as follows.（1）A sandwich structure MOFs composite ZIF-67@rGO with good electrical conductivity was constructed by doping reduced graphene oxide（rGO）with excellent electrical conductivity in cobalt-based zeolite imidazole salt framework（ZIF-67）through a one-pot hydrothermal reaction,with bisphenol A detection concentration range of 0.05μmol·L^-1 to 100μmol·L^-1.Compared with the same ratio of ZIF-67 and rGO physical mixture,the sandwiched structure of ZIF-67@rGO exhibited better electrocatalytic performance with a large electrochemically active surface area,high sensitivity and low detection limit of 5.2 nmol·L^-1（S/N=3）.（2）Cu-CAT@rGO,a copper-catecholate（Cu-CAT）with conductive organic ligands linked to oxidizing metal copper ions as the center,and synergistic conductivity with rGO were used to construct a MOFs composite with better conductivity,Cu-CAT@rGO,for the construction of bisphenol A electrochemical sensor（Cu-CAT@rGO/GCE）.The differential pulse voltammetry（DPV）technique was applied to electrochemical sensing for the detection of bisphenol A in beverage bottles with a linear detection range of 0.05μmol·L^-1 to 100μmol·L^-1 and a low detection limit of 4.9 nmol·L^-1（S/N=3）.（3）A sensitive sensor for measuring bisphenol A（Cu-H-T@rGO/GCE）was constructed by coordinating two organic ligands with conductivity,2,3,6,7,10,11-hexahydroxytriphenyl（HHTP）and tetrahydroxy-1,4-quinone（THQ）,and the type and ratio of the central metal ion to screen the MOFs composite Cu-H-T@rGO with further conductivity,and the results showed that the oxidation current of bisphenol A on the surface of the newly modified electrode was much higher than that of that of GCE.The linear detection range of Cu-H-T@rGO/GCE is 0.05μmol·L^-1-100μmol·L^-1 with a lower detection limit of 3.6 nmol·L^-1（S/N=3）.（4）MOFs materials with different conductive properties can be obtained by changing the type of metal ions（screening out Fe）or controlling the type of organic ligands（screening out HHTP and 2,3,6,7,10,11-hexaaminotriphenylene（HITP））,and excellent intrinsically conductive MOFs-Fe-HTP-HITP were synthesized by self-assembly to construct very sensitive sensors（Cu-H-T@rGO/GCE）for the measurement of bisphenol A.It was shown that when HHTP:HITP was 4:4,the best performance of Fe-HTP-HITP material was fabricated.Under the optimized conditions,the oxidation peak current showed a good linear relationship with the concentration of bisphenol A in the range of 0.05μmol·L^-1-150μmol·L^-1,and the detection limit was further reduced to0.9 nmol·L^-1.The four constructed MOFs materials ranged from intrinsically non-conductive to conductive,from monoligands to biligands,from doped composites to undoped pure MOFs electrochemical sensors and were applied to the detection of bisphenol A in food contact materials with progressively lower detection limits.These methods can provide good ideas for the development and application of MOFs,and provide new detection technology routes for food safety detection.