Determination Of Levodoap By Electrochemical Method

Levodopa(L-Dopa)belongs to catecholamine substance.It has amino and catechol(benzene with two hydroxyl groups)structure,and plays an important role in the human cardiovascular activity and neuroendocrine regulation.Dopamine(DA)is also the chemical neurotransmitters of stimulating,and belongs to the catecholamine.DA plays an important role in the central nervous,renal,hormonal and cardiovascular system function,and the abnormal concentration of dopamine in the human body often causes many diseases,for example,senile dementia,epilepsy and Parkinson's disease(PD).Levodopa(L-Dopa)is a metabolic precursor of DA,and is mainly used for the treatment of Parkinson's disease.It can enter the brain through the blood-barrier,and transform into DA in the brain,so as to supplement the DA in the brain,and relieve the symptoms of Parkinson's disease.As both DA and L-Dopa have important physiological function and clinical application,the research on them is more and more widely in recent years.Thus it is necessary to establish a simple,rapid and accurate analysis method of L-Dopa.Because L-Dopa has electrochemical activity,it can be measured by electrochemical method.The interference of ascorbic acid(AA)is the greatest difficulty for electrochemical determination of L-Dopa in the presence of AA.AA and L-Dopa are often coexist in the brain and body fluids,the concentration of AA is far higher than the concentration of L-Dopa.AA and L-Dopa occur redox reaction at nearly the same potential on the bare electrode.How to measure the content of L-Dopa in the presence of high concentration of AA has become one of the most important subjects of electrochemical analysis.AA has a feature that it will lose electrochemical activity after it was oxidated,while L-Dopa still has electrochemical activity after it was oxidated.This experiment takes advantage of the feature to add a certain amount of oxidant to the mixed solution of AA and L-Dopa and to use bare glassy carbon electrode by cyclic voltammetry method and differential pulse method to determine Levodopa in a high concentration of ascorbic acid solution.The oxidant has no any interference for the measurement L-Dopa.Using cyclic voltammetry(CV)method,the reduction current is well linear with L-Dopa concentration in the range of 5×10-5 mol/L?3 x 10-6mol/L.While using differential pulse voltammetry(DPV)method,the reduction current is well linear with L-Dopa concentration in the range of 5×10-5 mol/L?5×10-7mol/L.This method has the following advantages:Both Levodopa and ascorbic acid have electrochemical activity.We eliminated the interference from AA completely,depending on whether their electrochemical activity keeps or not after being oxidized.It is the first time to determinate the L-dopa in the presence of high concentrations of AA with bare glassy carbon electrode.Some Chemical modified electrodes have poor reproducibility due to their complicated manufacturing process,while bare glassy carbon electrode has better reproducibility.Some modified electrodes only can be used within a certain range of concentrations of levodopa and ascorbic acid,while this method completely eliminates interference from AA,and its range of application is wider.What'smore,this experimental method has the advantages of simple operation?high sensitivity‘strong anti-interference ability.It is a good way for accurate determination of L-Dopa in the presence of AA.