Study On Modified Electrode Based On Pencil Lead And Electrochemical Detection Of Phenol In Water

Electrochemical sensors prepared with chemically modified electrodes have attracted researchers’attention due to their high detection sensitivity,simple operation,cheap equipment and rapid detection.This project develops pencil lead as the base material to prepare pencil graphite electrode.The specific work includes the following four parts:（1）The preparation method of a new pencil graphite electrode was studied to evaluate the influence of physical factors such as the brand of electrode substrate,the type of pencil lead,the sensing area and length on the electrochemical performance of the electrode.The 2mm diameter pencil lead of tianzhuo brand HB was selected and the 3 cm length pencil graphite electrode was prepared.Physical treatment of the electrode can improve the reversibility of the electrode.Electrochemical treatment of pencil graphite electrode with cyclic voltammetry and constant potential method above 1.3 V potential can activate the electrode,improve the reversibility of the electrode,and enhance the electron transmission rate.The potential range of cyclic volt-ampere method was 1.3¹.9 V,the sweep speed was100 mV/s,and the potential was 1.4 V when the number of cycles of scanning was 50,and the treatment time was 60 s.0.8 mol/L NaOH solution was used as electrode electrochemical treatment solution.The electrochemical detection of potassium ferocyanate and bisphenol A at the same geometrical sensing area was compared between the glassy carbon electrode and the pencil graphite electrode.The antipollution ability of glassy carbon electrode and pencil graphite electrode was compared,and graphite electrode has better antipollution ability than glassy carbon electrode.（2）Through a simple hydrothermal method the alpha MnO₂ nanometer metal oxide,and scanning electron microscope,XRD,CV to characterize,and preparation of the NaOH/α-MnO₂/CS modified electrodes,its effective area compared with the bare pencil graphite electrode increases for 2 times,resulting in NaOH/α-MnO₂/CS electrode electrochemical response improved significantly,the cyclic voltammetry of NaOH/α-MnO₂/CS modified electrode was tested,and it was found that the material had good electrochemical reversibility.（3）NaOH/pencil graphite electrode was constructed to detect naphthol directly.The irreversible oxidation reaction of naphthol on the surface of NaOH/pencil graphite electrode was controlled by adsorption and fluctuated near the peak potential of 0.4 V.When PB buffer solution with pH=6.0,enrichment potential 0.0 V,and enrichment time 80 s,naphthol showed the maximum voltammetry response current.There was a good linear relationship between two concentration ranges of 25¹50μmol/L and 150³75μmol/L,with a sensitivity of 0.0106μmol/M and A detection limit of 0.308μmol/L.The relative standard deviations of the repeatability and reproducibility of NaOH/pencil graphite electrode were1.94%and 2.73%respectively,showing good repeatability and reproducibility.NaOH/pencil graphite electrode shows good selectivity and anti-interference performance in anti-interference experiment.The standard recovery rate of naphthol was 103.42%,and the electrochemical detection method of naphthol was reliable.（4）NaOH/α-MnO₂/CS modified electrode was constructed to directly detect bisphenol A.An irreversible oxidation reaction of bisphenol A on the electrode surface was controlled by adsorption,and the peak potential of bisphenol A fluctuated near 0.536 V.When PB buffer solution with pH=7.4,enrichment potential of-0.4 V,enrichment time of 35 s,andα-MnO₂/CS drop coating amount of 6μL,the maximum volt-ampl response current of bisphenol A appeared.which had a good linear relationship in the concentration range of10¹20μmol/L,with a sensitivity of 0.0388μmol/M and a detection limit of 0.0234μmol/L.NaOH/α-MnO₂/CS modified electrode showed good stability,repeatability and reproducibility.The average recovery rate of bisphenol A was 98.92%,which indicated that the method had good reliability.The establishment of NaOH/α-MnO₂/CS modified electrode provides a new research idea for the electrochemical detection of bisphenol A.