Study Of Novel Chemically Modified Electrodes For Gallic Acid Detection

Gallic acid,a natural polyphenol,is one of the main phenolic components of plants such as black tea and grapes.It is widely used in the fields of food,medicine,chemical industry and cosmetics because of its anti-oxidant,antibacterial,antiviral,and other functions.The values obtained for gallic acid can be used as the quality evaluation standard of green tea and black tea based on gallic acid oxidation.However,excessive intake of gallic acid in the human body can cause irreversible damage to the kidney and cause cytotoxicity.At present,most of the current methods for detecting gallic acid are based on high performance liquid chromatography,gas chromatography,etc.,which have the shortcomings of complex operation process and expensive instruments.But the operation process is complicated and the instruments are expensive.Therefore,research and establishment of fast and accurate gallic acid detection methods are of great significance to ensure food safety and quality and maintain human health.Electrochemical detection method based on chemically modified electrode has become an important development direction in the field of food additive detection such as gallic acid because of its low price,simple operation and fast detection speed.Based on this frontier and focus area,this paper investigates the design of novel modified electrodes to provide a potential solution for the development of highly sensitive,convenient and fast gallic acid detection methods in view of the shortcomings of the current research used for gallic acid electrochemical detection,such as complex modification,long time consuming and low sensitivity.The research content and main research results of the paper are as follows.（1）Electrochemical detection of gallic acid based on polyethylene imine-electrochemical reduction graphene oxide modified glassy carbon electrod.In this experiment,the glassy carbon electrode was selected as the base electrode.The polyethylene imine-graphene oxide dispersed droplets were coated on the surface of the glassy carbon electrode by the drop coating method,and then electrochemically reduced in phosphate buffer solution to prepare the polyethylene imine-electrochemical reduction graphene oxide modified glassy carbon electrode（PEI-Er GO/GCE）.A direct determination of gallic acid was achieved at a glassy carbon electrode modified with polyethylene imine-electrochemical reduction graphene oxide under differential pulse voltammetry conditions and cyclic voltammetry conditions.The conditions of electrode surface loading,buffer p H and reaction rate were optimized by using a simple one compartment three-electrode cell.Gallic acid at the modified electrode shows an irreversible well-defined adsorption-controlled redox CV wave.Under the optimum experimental conditions,the linear range of gallic acid detection by this electrode is from0.1 to 40μM with a correlation coefficient of 0.9973.The new electrochemical sensor established in this experiment has good anti-interference and wide linear range.In the actual sample,the recovery rate of spiking is from 95.3%to 109.7%,and the relative standard deviation is from 3.2%to 4.5%.The PEI-Er GO/GCE sensor can be used to detect the content of gallic acid in the actual sample with high accuracy.In this experiment,we proposed a one-step electrochemical reduction method to prepare PEI-Er GO/GCE modified electrode with excellent catalytic effect on the electrochemical oxidation of gallic acid,and based on this method,we developed a simple and sensitive electrochemical sensor for gallic acid detection.（2）Electrochemical detection of gallic acid based on poly（L-cysteine）modified glassy carbon electrode.The base electrode of this experiment is a glassy carbon electrode.Modification of glassy carbon electrode was done by electropolymerization of L-cysteine,L-cys,in 0.2 M phos-phate buffer solution using cyclic voltammetry,CV.The experiments were characterized by cyclic voltammetry,a negatively charged potassium ferricyanide ion([Fe（CN）₆]^3-)probe and a positively charged hexaamminoruthenium ion([Ru（NH3）₆]³⁺)probe.A three-electrode system was used to study the response of gallic acid at the modified electrode using cyclic voltammetry and differential pulse voltammetry,and the conditions of membrane thickness,buffer p H,and reaction rate were optimized by using a simple one compartment three-electrode cell.Under the optimal conditions of the experiment,the concentration of gallic acid showed a good linear relationship with the oxidation peak current in the range of 0.1μM to 40μM,with a correlation coefficient of0.9956.The recovery of gallic acid in canned fruit samples within the range of 90.9%～110%that strongly support high applicability of present method for real samples analysis（<5.0%RSD）which candidate this method as promise for further application.So this method can be applied to the determination of gallic acid content in the actual sample.So this method can be applied to the determination of gallic acid content in the actual sample.The new electrochemical sensor established in this experiment and the standard deviation of the results of six experiments using repeatedly was 2.5%with high stability,indicating that the contamination of gallic acid on p L-cys/GCE was lower than that on PEI-Er GO/GCE,and the p L-cys/GCE electrode was simple to prepare,with good stability and anti-interference,and had a wide linear range,low detection limit and high sensitivity.The p L-cys/GCE modified electrode constructed in this experiment has better anti-pollution performance than the PEI-Er GO/GCE modified electrode in the first study,and the preparation process is simpler.