Electrochemical Detection Of Uric Acid And Dopamine With Polymer Film Modified Electrodes

Uric acid(UA)and dopamine(DA)are electroactive substances with important biological research value,which usually coexist in the blood and urine of human.UA and DA are important in maintaining normal metabolism of human body,abnormal concentrations of the two substances often lead to the corresponding diseases.Therefore,the detection for concentrations of UA and DA in human body is of great practical value for the prevention and treatment of related diseases.However,other electroactive substances co-existing with UA and DA in human body,such as ascorbic acid(AA)and reduced nicotinamide adenine dinucleotide(NADH),are similar to the electrochemical activities of UA and DA.Whereas,conventional electrodes are difficult to eliminate interference and selectively detect UA and DA.The polymer film modified electrodes can utilize the characteristics of polymer films to make the electrodes have the advantages of reliable selectivity,high sensitivity,and strong stability.Therefore,in this paper,electrochemical methods are used to modify the polymer films with selective permeability and good electron conductivity on the surface of screen-printed carbon electrode strip(SPCEs).The electrochemical properties of different polymer films modified electrodes were investigated by analyzing the electrochemical responses of UA and DA on the modified electrodes.The main contents are as followings.1.Nafion/SPCEs was prepared by potentiostatic electrodeposition method,and the thickness of Nafion film was controlled at micron scale.The thickness of different layers Nafion films was measured by 3D optical profilometer.The layers of Nafion film were optimized by analyzing the results of impedance analyzer and electrochemical workstation.Based on the cation selective permeability of Nafion,Nafion/SPCEs successfully excluded the interference of AA and NADH,and realized the selective detection of UA.The linear detection range of UA concentration was 62.5~5000?M(R~2=0.9987),and the detection limit was 20.8?M(S/N=3).The detection performance of Nafion/SPCEs was consistent with that of colorimetry.The main advantages of Nafion/SPCEs are no requirements of enzyme reagents and acid environment,simple preparation process,and less equipment,which make the selective detection of UA more convenient.2.Poly L-lysine(PLL)modified SPCEs(PLL/SPCEs)was prepared by electrochemical polymerization.According to the detection results of impedance analyzer and electrochemical workstation,the layer number of PLL film was optimized.The results showed that PLL/SPCEs could be successfully used for the parallel detection of UA and DA in the mixed solution,and had a good linear relationship between the peak currents and the concentrations of UA and DA.The linearity range of UA and DA was 31.2~2000?M(R~2=0.9872)and7.8~500?M(R~2=0.9653),and the detection limits of UA and DA were 10.4?M(S/N=3)and 2.6?M(S/N=3),respectively.3.Nafion/PLL/SPCEs was fabricated by electrochemical polymerization and electrodeposition method.The electrochemical behavior of UA,DA and AA on the electrode was studied by cyclic voltammetry.The results showed that Nafion/PLL/SPCEs could effectively eliminate the interference of ascorbic acid and realize the selective detection of UA and DA.The peak currents of UA and DA showed a good linear relationship with their concentrations.The linear ranges of UA and DA were 125.0~4000?M(R~2=0.9793)and7.8~250?M(R~2=0.9659),respectively.