| Analysis and testing are indispensable in the process of research and development,production,circulation and use of drugs,which is an important link to ensure the quality of drugs.In addition,medical examination is very meaningful for clinical diagnosis of diseases and rational use of drugs.At present,many detection methods have been applied,mainly including spectrophotometry（UV）,capillary electrophoresis（CE）,fluorescence,colorimetry,high performance liquid chromatography（HPLC）,titration and electrochemical methods.Electrochemical analysis is an analysis method based on the electrochemical properties of substances in solution.The content of substances can be obtained by measuring some physical changes of batteries,among which the commonly used physical quantities are potential,current and conductivity.Compared with other analytical techniques,electrochemical detection method has broad application prospects because of its advantages of simple equipment,high sensitivity,low detection limit,wide linear range,low sample consumption and high selectivity.Electrochemical analysis,as an analytical method,has been widely used in the field of medical detection.The focus of research in electrochemistry is electrochemical sensor,and the important factor that determines the detection performance of sensor is the construction of electrode modification materials of electrochemical sensor,which is the most important research of electrochemical sensor at present.In this paper,graphene,multi-walled carbon nanotubes and nano silver are used as modified materials to construct two kinds of electrochemical sensors,which are analyzed by cyclic voltammetry and differential pulse voltammetry.Based on this,the electrochemical detection of anticyclonic acid,uric acid and acetaminophen was realized respectively.The main research contents and achievements are divided into the following parts:1.Preparation of graphene modified electrode and establishment of electrochemical method for determination of ascorbic acid.Reduced graphene oxide modified glassy carbon electrode（ERGO/GCE）was prepared by one-step electrodeposition using electrochemical reduction technology,and the electrochemical behavior of ascorbic acid（AA）on the modified electrode was studied by cyclic voltammetry.The results showed that the prepared reduced graphene oxide modified electrode had a significant electrocatalytic effect on ascorbic acid compared with bare glassy carbon electrode.Using phosphate buffer solution（pH=6.5）as the test base solution,an irreversible oxidation peak appeared in the scanning potential range of-0.4 V～0.8 V for AA.Under the optimized experimental conditions,in the concentration range of 1.7×10-3mol/L～2×10-5mol/L,the oxidation peak current of AA has a good linear relationship with the concentration change,the correlation coefficient is 0.991,and the detection limit is 9×10-6mol/L（S/N=3）.The stability and anti-interference of the modified electrode were studied.The results showed that the electrode had good stability and strong anti-interference ability.The modified electrode was used to detect AA content in tablets,and the recovery rate was between97.50%and 100.58%.The electrochemical method established in this paper can be applied to the determination of AA in tablets with satisfactory results.2.ERGO modified electrode was prepared by one-step electrodeposition,and the electrochemical performance of uric acid on this modified electrode was studied by cyclic voltammetry（CV）.After optimizing the experimental conditions and parameters,the experimental results showed that this modified electrode had obvious electrocatalytic effect on the oxidation of uric acid compared with bare glassy carbon electrode.The concentration of uric acid is in the range of 9.0×10-4mol/L～7.0×10-5mol/L,under the optimized experimental conditions,and the peak current has a good linear relationship with the concentration of uric acid,with the lowest detection limit of 1×10-6mol/L..Using ERGO/GCE modified electrode,the recovery rate of UA was between 99.38%and101.40%.The constructed sensor has stable performance,good reproducibility,strong selectivity to UA and certain anti-interference ability.It can be used for quantitative detection of UA.3.Using electrochemical reduction method,reduced graphene oxide was prepared by one-step electrodeposition.An electrochemical sensor with graphene as electrode modification material was constructed and used for the analysis and detection of acetaminophen.The electrochemical behavior of acetaminophen at the modified electrode was studied by cyclic voltammetry（CV）and differential pulse voltammetry（DPV）.The experimental results show that reduced graphene oxide modified glassy carbon electrode has good electrochemical catalysis for acetaminophen in PBS buffer solution（pH=7）.Acetaminophen showed a pair of obvious redox peaks on the modified electrode.Under the optimized experimental conditions,in the concentration range of 5.0×10-8mol/L～1.0×10-4mol/L acetaminophen,the oxidation peak current of acetaminophen showed a good linear relationship with its concentration,and the lowest detection limit（S/N=3）was 3.0×10-8mol/L.The modified electrode was used to detect acetaminophen in tablets,and the recovery rate was between 97.03%and 99.94%.The electrochemical sensor constructed with graphene has good stability,high detection sensitivity and significantly enhanced selectivity.It can be used to detect the content of acetaminophen in tablets.4.Oxidizing multi-walled carbon nanotubes with mixed acid to prepare carboxylated multi-walled carbon nanotubes.The nano silver/multi-walled carbon nanotube composites（Ag NPs/MWCNTs）were prepared by ethylene glycol reduction.The electrochemical behavior of ascorbic acid on Ag NPs/MWCNTs/GCE was studied by cyclic voltammetry.the results show that multi-walled carbon nanotubes can be uniformly dispersed in water solvent after mixed acid treatment.the nanocomposite modified electrode has better electrocatalytic performance than MWCNTs/GCE.the effects of pH value of buffer solution and scanning speed on the electrochemical activity of ascorbic acid were investigated.Under the optimized conditions,in 0.2 mol/L phosphate buffer solution（pH=7.0）,differential pulse voltammetry was used in the potential range of-0.2 V～0.1 V,and the concentration of ascorbic acid was in the range of 1.0×10-2mol/L～5.0×10-4mol/L,and the oxidation peak current was linearly related to the concentration change,with the lowest detection limit The method is applied to the determination of ascorbic acid in vitamin C tablets,and can quickly and accurately determine its content.And the recovery rate is between 96.05%and 101.51%.This study provides a new idea for the detection of ascorbic acid. |
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