| At present, as an important means of analysis, electroanalytical method has been widely used in many fields. And chemically modified electrode(CME) is the most important tool in electrochemical analysis, in which the use of CME can improve the sensitivity, selectivity, stability and exhibit unique superiority. From the perspective of methodology in electrochemical analysis, no new method presents in recent years. So, the attention is mainly focused on the construction of the new CME to improve their sensitivity, selectivity and stability in real analysis. In order to obtain good performance of CME, a lot of new materials and electrode preparation technologies have sprung up. Based on this idea, we mainly employed amino acids, graphene, graphene oxide and carbon nanotubes(CNTs) as electrode modified material to build a series of CME to improve its voltammetric sensitivity, selectivity and stability in determination of some important drug molecules.(1) The construction and characterization of chemical modified electrodesThe microstructure and element distribution of electrode surface can be changed by the process of electrochemical treatment. Therefore, the changes of the electrochemical performance from the interface and surface groups were investigated before and after the introduction of oxygen containing functional groups. Then, amino acids, graphene, polymer Nafion were selected as modified materials, and a series of poly(amino acid), poly(amino acid)/graphene and graphene- Nafion modified electrodes were fabricated by simple dipping-drying/electrochemical polymerization or combination of these two methods. The electrochemical properties and characterization of these CMEs were studied to figure out the different effect on the electrochemical performance derived from the different modified material. Finally, the graphene oxide prepared by chemical oxidation method. Thereafter, the electrochemically reduced graphene oxide in situ and reduced CNTs doped graphene oxide in situ on the electrode surface were obtained. The electrode surface morphology and the electrochemical properties were investigated in detail. Meantime, the differences of electron transport properties among carbon materials was preliminarily compared. The results indicated that the oxygen and nitrogen groups introduced on glassy carbon electrode surface hindered electron transfer of the probe K3[Fe(CN)6] to electrode surface, whereas carbon materials such as graphene, CNTs can accelerate the electron transfer.(2) Voltammetric sensing application of the proposed CMEs in pharmaceutical analysisThe important purpose of constructing the CMEs is to improve the sensitivity, selectivity and stability of the working electrode, and then realize their analytical applications. Therefore, some important electroactive drug molecules were as model and their electrochemical behaviors were investigated in detail on proposed CMEs above. Different electrochemical techniques were used to establish analytical methods to implement the application purpose. At first, the electrochemical behavior of jatrorrhizine at electrochemically pretreated glassy carbon electrode was systematically discussed in detail and some kinetic parameters were calculated for the first time. A reasonable reaction mechanism of jatrorrhizine was also discussed and proposed, which could be a reference for the pharmacological action of jatrorrhizine in clinical study. And the first electroanalytical method of jatrorrhizine was established. The proposed method was successfully applied in determination of jatrorrhizine in pharmaceutical sample, Tinospora capillipes Gagnep(a traditional Chinese medicine). Then, on the basis of sufficient investigating the interface characterization of poly(amino acid), poly(amino acid)/graphene and graphene-Nafion modified electrodes, the electrochemical behaviour of some important drug molecules including sophoridine, bergenin and codeine were investigated. And the corresponding electroanalytical methods were also erected. After the comparison of electron transfer difference between carbon materials, the in situ-electrochemical reduction of graphene oxide modified electrodes and in situ-electrochemical reduction of CNTs doped graphene oxide modified electrodes were used in the determination of morphine, esculetin and Polydatin, which further expanded the application prospect of graphene modified electrode in pharmaceutical analysis.Results showed that although the oxygen and nitrogen functional groups on the electrode surface prevented the electron transfer of K3[Fe(CN)6], the above mentioned modified electrodes displayed significant enhancement of electrochemical response and selectivity for the analyte studied. And they were successfully applied to the analysis of real samples. In a word, due to the excellent electron transfer performance and large specific surface area of graphene and CNTs, they not only accelerated electron transfer of the probe K3[Fe(CN)6], but also contributed to promote electrochemical reaction rate of the object to be analysed; Meanwhile, large specific surface area has increased the amount of preconcentration of the analyte on electrode surface, which enhanced the electrochemical response signal. Therefore, the sensitivity is improved. |
