Study On Phenols Using Nano-Micro Electrochemical Sensor

Phenolic compounds are widely found in nature,which not only affect the physiological functions of plants,but also have an important impact on human health,especially many diseases.In addition,phenols also have significant effects on food antioxidants,deodorization,flavor adjustment,and clarity adjustment.Therefore,the determination of the content of phenolic compounds and the monitoring of metabolic processes in vivo have important practical significance.Phenols and their metabolites or isomers are similar in structure,which are difficult to distinguish and separate in analysis and measurement,and easily interfere with each other,which brings certain difficulties to the qualitative determination of a single substance.The phenolic compound has a hydroxyl electroactive group and is prone to redox reaction.However,similar structures of isomers and metabolites tend to have similar redox potentials,which are not well separated on solid large electrodes and cannot be measured simultaneously.In this thesis,several novel nano-electrochemical sensors have been constructed,which modify carbon fiber microelectrodes(CFE)with electroactive graphene oxide(GO),multi-walled carbon nanotubes(MWCNTs),metal nanoparticles and conductive polymers.The modified nano-electrochemical sensor is small in volume,fast in response and high in sensitivity,and can be used for on-line determination of several groups of phenolic compounds in plant animals.The main contents of this paper are as follows: 1.Electrochemical behavior of three dihydroxybenzoic acid isomers on pRGO-MWCNTs/AuNPs/CFE and its application.A gold nanoparticle sensitized partially reduced multilayer graphene oxide-multiwall carbon nanotube modified carbon fiber microelectrode(pRGO-MWCNTs/AuNPs/CFE)was prepared and used to simultaneously determine three dihydroxybenzenes.Formic acid isomers(DHBAs),namely 2,3-DHBA,2,5-DHBAB and 2,6-DHBA.Cyclic voltammetry(CV)showed that the three DHBAs were well separated on the pRGO-MWCNTs/AuNPs/CFE nano-electrochemical sensor and had good electrochemical response.2,3-DHBA,2,5-DHBAB and 2,6-DHBA were separately and simultaneously determined by differential pulse voltammetry(DPV).When DHBAs are present alone,the linear ranges of 2,3-DHBA,2,5-DHBA and 2,6-DHBA are 4-6000 nM,2-2000 nM and 40-4000 nM,respectively,with detection limits of 0.25 nM,respectively.0.10 nM and 2.70 nM(S/N = 3).The linear ranges measured by the three were 8-9000 nM,8-8000 nM and 20-2000 nM,respectively,and the detection limits were 0.34 nM,0.55 nM and 1.30 nM(S/N = 3),respectively.The sensor has good repeatability,stability,precision and anti-interference performance,and has been successfully applied to monitor the change of DHBAs content in the roots of spider stalks in real time.2.Electrochemical behavior of 4-hydroxybenzoic acid and its metabolite 3,4-dihydroxybenzoic acid on PEDOT-PSS/CoPc/CFE and its application.Poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid(PEDOT-PSS)and cobalt phthalocyanine(CoPc)were modified on the carbon fiber electrode(CFE)by electrodeposition in turn and the resulting modification was carried out.The electrode was used to determine 4-hydroxybenzoic acid(4-HBA)and its metabolite 3,4-dihydroxybenzoic acid(3,4-DHBA).CV showed that 4-HBA and its metabolite 3,4-DHBA were well separated on PEDOT-PSS/CoPc/CFE and had good electrochemical response.4-HBA and its metabolite 3,4-DHBA were determined separately and simultaneously using DPV.When 4-HBA and 3,4-DHBA were present alone,the oxidation peak current of 3,4-DHBA showed a good linear relationship with the concentration in the range of 0.2-10.0 μM,and the detection limit was 6.0 nM.The oxidation peak current of 4-HBA has a good linear relationship with the concentration in the range of 0.2-10.0 μM,and the detection limit is 8.0 nM.The linear ranges of 3,4-DHBAs and 4-HBA were 0.6-10 μM and 0.6-10 μM,respectively,and the detection limits were 50.0 nM and 92.0 nM,respectively(S/N = 3).4-HBA acts as a capture agent for hydroxyl radicals to produce the only product,3,4-DHBA.By the simultaneous detection of 3,4-DHBAs and 4-HBA,the content of 4-HBA is observed and passed through 3,4-The content of DHBA reflects the content of hydroxyl radicals.This sensor is finally used for the determination of hydroxyl radicals in blood samples.3.Electrochemical behavior of apigenin and baicalein isomers on LaNPs-CoNPs/CFE and its application.A LaNPs-CoNPs bimetallic structure was formed on the CFE by electrodeposition,and the nanoelectrode was used for the determination of apigenin and baicalein.CV showed that apigenin and baicalein were well separated on LaNPs-CoNPs/CFE and had good electrochemical response.Apigenin and baicalein were measured separately and simultaneously using DPV.When apigenin and baicalein were present alone,the linear range of oxidation peak current and concentration of baicalein was 0.01-1.00 μM,and the detection limit was 1.2 nM.The oxidation peak current and concentration of apigenin have a good linearity in the range of 0.2-10.0 μM,and the detection limit is 11.1 nM.The linear range of the two measurements was 0.04-1 μM and 0.05-1 μM,respectively,and the detection limits were 2.1 nM and 2.7 nM(S / N = 3),respectively.The sensor realized the content distribution of baicalein and apigenin in mice.