Preparation Of Polymer Modified Electrode And Its Application In The Determination Of Biomolecules

Dopamine (DA) is an important neurotransmitter in the type of catecholamine. and has a significant influence on the transmitting of signals in nervous system of mammal. Its concentration in organism influences multiple physiological processes, and the change of content can cause some serious diseases, such as schizophrenia, Parkinson’s disease; uric acid (UA) is the end product of catabolic process of purine nucleotide in the body, content change of uric acid in body fluid can fully reflect the condition of functions as metabolism and immune of human body, and can also indirectly reflect the disease related to purine metabolism, such as gout, leukemia and pneumonia, etc:tyrosine (Tyr) is one of important components of protein, possessing an essential function of maintaining a balanced nutrition of human body, and the unbalance of tyrosine will cause some disease as albinsim. aicaptonuria, depressive disorder and other psychological illness; tryptophan is an important amino acid, which is widely used in medicine, food and feed additive fields. In addition, Trp is also the precursor of5-hydroxytryptamine. an important neurotransmitter of human body, and has an important function of treating depressive disorder, insomnia, and reducing arthralgia, neuralgia, and courbature, but excessive tryptophan will cause some negative effects on human body and animaL such as diarrhea, lever and nausea, etc. By this token, the accurate measurement of DA, UA, Tyr and Trp has a great significance. And this topic is about accurately and sensitively measuring the content of DA, UA, Tyr and Trp in biological samples.Lots of people in China and abroad are studying the measurement of DA. UA. Tyr and Trp, and there are several frequently-used analytical methods to detect those substances, such as spectrophotometry, chromatography. chemiluminescence and capillary electrophoresis, etc. Those methods have their own advantages as fast analysis speed and simple analytical method, etc, but they all have one disadvantage in common: expensive instrument and equipment. While electrochemistry is also a very important analytical method, and the instrument used is relatively inexpensive, and easy to operate, and has a high sensitivity. Especially the polymer modified electrode is getting more attention because it has more advantages, such as better stability, higher catalytic activity, stronger selectivity, and thickness on the surface of the electrode is controllable, etc.There are three kinds of polymer modified electrode in the three parts of work in this article, and to research separately their testing effectiveness about DA. UA, Tyr and Trp. This method is easy to operate and of low cost, meanwhile il gains lower detection limit, higher sensitivity and better selectivity in the process of measuring analyte.The work of this article is mainly divided into three parts as following:1. This article has prepared glassy carbon electrode (PABSA/GCE), which is modified by Poly-aminobenzene sulfonic acid, and has taken the method of differential pulse voltammetry (DPV), and has applied it in the simultaneous determination of dopamine, uric acid and tyros ine.Electrochemistry impedance (EIS) and cyclic voltammetry (CV) are both used in studying nanometer net polyaniline-glassy carbon electrode (PABSA/GCE) modified by PoAP composite membrane. Compared to GCE, GCE modified by PABSA composite membrane shows a better electrochemical activity, and shows a good selectivity and sensitivity to the simultaneous determination and selective determination of UA and Tyr. Since UA and Tyr show: different electrochemical response, either cyclic voltammetry (CV) or DPV, PABSA/GCE can divide the anodic peak which is the overlapping parts of DA and UA into two completely separated volt-ampere peak and can increase peak current response value. Linear growth of DPV peak current value is between range0.05～230μmol/L and0.08～300umol/L according to the concentration of UA and Tyr, and coefficient of association are0.9990and0.9991. Limit of detection (3σ) of UA and Tyr are0.05and0.08μmol/L. PABSA/GCE shows good reproducibility and stability, which is used in the measurement of UA and Tyr and obtains satisfactory result.2. Adopt cyclic voltammetry (CV) to modify sulfosalicylic acid (PSA) on the surface of glassy carbon electrode (GCE) for glassy carbon electrode modified by sulfosalicylic acid (PSA/GCE). And it is successfully used in the simultaneous determination of DA, UA and Tyr. The results show that, glassy carbon electrode modified by sulfosalicylic acid can not only improve electrochemical behavior of DA, UA and Tyr, but can also divide the overlapping anodic peak into three obvious and sharp anodic peaks. Peak potential difference of DA and UA is160mV, and peak potential difference of UA and Tyr is320mV, therefore this modified electrode can be used in the simultaneous determination of DA, UA and Tyr in mixed liquor. Under optimized experiment conditions, oxidation peak current of DA, UA and Tyr concentration are in good linear relation with the concentration within the range of0.1-115、1-235and0.1-390μmol L-1, coefficient of association are0.9980,0.9969and0.9989, detection limit (S/N=3) are0.05μmol L-1、0.3μmol L-1and0.08μmol L-1. In phosphate buffer solution (PBS), PSA/GCE shows good electro catalytic activity, and electrochemical reaction process of electrode surface is a surface control electrode process. This modified electrode has a high reproducibility and a strong stability, with good selectivity, higher sensitivity and wider detection range. Apply it in the simultaneous determination of DA, UA and Tyr in urine and in serum sample, a satisfactory result is gained.3. Compound composite membrane of3,4-ethylenedioxythiophene (EDOT) and o-phenylenediamine (OPD) on glassy carbon electrode (GCE), and use this composite membrane into the simultaneous determination of tryptophan and tyrosine with differential pulse voltammetry method. Adopt electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) to study glassy carbon electrode modified by composite membrane of3,4-ethylenedioxythiophene (EDOT) and o-phenylenediamine (OPD)(PEDOT-OPD/GCE), and results show that PEDOT-OPD membrane has good electrochemical activity. In the determination of Trp and Tyr, compared to naked GCE, EDOT modified electrode and OPD modified electrode, GCE modified by PEDOT-OPD composite membrane shows better sensitivity and selectivity, and using cyclic voltammetry (CV) can reduce overpotential of Trp and Tyr by70mV and60mV and improve current response value. The linear growth of DPV peak current value is between range0.06-220μmol L-1and0.1-250μmol L-1according to the concentration of UA and DA. limit of detection (3σ) and coefficient of association of UA and DA are0.006μmol L-1和0.05μmol L-1,0.9950and0.9958. PEDOT-OPD/GCE shows good reproducibility and stability, which is used in the determination of Trp and Tyr under the coexistence of DA and UA.