The Preparation Of Modified Electrodes With Carbon-Based Nanocomposites And Their Application In Pharmaceutical Analysis

Pharmaceutical analysis, an important branch of analytical chemistry, has gradually become an independent discipline with the development of pharmacy. From now on, research area and analytical methods of pharmaceutical analysis have been developed greatly. Electrochemistry, as a tool of analytical chemistry, has extensive application. Invention of various microelectrodes, modified electrodes, electrochemical sensors, owing their outstanding features such as high sensitivity, fast response and simple instrumentation, gives pharmaceutical analysis new energy and power. As the development of electrochemical analysis, the application of electro-chemical analysis is becoming wider and wider. It also plays a more and more important role in drug development and pharmaceutical production. In this paper, we have prepared different electrodes modified dessertation for the analysis of drugs which can summarized as follows:1. A novel nanocomposite modified electrode（Co₃O₄/GR/GCE） based on graphene（GR） with tricobalt tetroxide nanoparticles nanocomposite film was prepared to determine isoniazid. The experiments show that electrocatalytic activity of isoniazid was highly improved compared with that on bare electrode. Scanning electron microscopy was carried out to characterize the nanocomposite film which exhibits graphene（GR） and tricobalt tetroxide nanoparticles were both distributed on the surface of glassy carbon electrode（GCE）. Experimental parameters were optimized by different pulse voltametry（DPV）. Under optimal conditions, the different pulse voltammograms exhibited that the oxidation peak current was linearly proportional to the concentration of isoniazid in the range of 0.5 160 μM with dection limit of 0.17 μM（S/N = 3）. Moreover, this method was applied to detect isoniazid in medicinal tablets and serum with satisfying results.2. Based on above work, cysteic acid-graphene nanocomposite modified electrode（GR/CA/GCE） was prepared by oxidizing L-cysteine was into cysteic acid which was deposited on the of graphene（GR） modified electrode by electrochemical technique. The GR/CA/GCE, used to detect isoniazid, can greatly improve the electron transfer process and decrease the impedance of the suface of the electrode. Compared with Co₃O₄ /GR/GCE, GR/CA/GCE has shown better experiment results. Under optimal experimental conditions, GR/CA/GCE exhibited wider linearity of 0.1 200 μM for isoniazid with detection limit of 0.03 μM（S/N = 3）. Moreover, this method was applied to detect isoniazid in medicinal tablets with satisfying results.3. A facile and novel preparation strategy based on electrochemical techniques for the fabrication of electrodeposited graphene（GR） and zinc oxide（ZnO） nanocomposite modified electrode（ZnO/GR/GCE） was developed to determine ofloxacin. The GR/CA/GCE can greatly enhance the electron transfer process and decrease the impedance of the suface of the electrode. At the same time, the oxidization of ofloxacin was highly increased on this modified electrode. Under the optimal experimental condtions, the experiment results exhibited that the oxidation peak current was linearly proportional to the concentration of ofloxacin in the range of 1 100 μM with the sensitivity of 1399.86 μA m M-1 cm2. The results of determination of ofloxacin in real samples demonstrate that this proposed method would be suitable for the routine analysis of ofloxacin in clinical use.4. Considering the excellent properties of newly nanomaterial multi-walled carbon nanotubes（MWCNTs）, MWCNTs-vitamin B12 nanocomposites modified glassy carbon electrode（MWCNT/VB12/GCE） was developed to detect p-Hydroxyacetophenone（p-Hyd）. Fourier transform infrared spectroscopy scanning electron microscopy were carried out to prove that MWCNTs and VB12 were modified on the surface of the glassy carbon electrode. Based on optimum conditions, the experiment result shows that, at the MWCNT/VB12/GCE, the current of ofloxacin is linearly related to its concentration in the range of 0.5 20 μM and 20 200 μM, respectively. Compared with poly（eriochrome black T） modified electrode, the oxidization peak of p-Hyd at MWCNT/VB12/GCE shifted negative by 0.04 V.5. A thin film of poly（eriochrome black T） was deposited on the surface of glassy carbon electrode by cyclic voltammetry for the sensitive determination of p-Hyd. Scanning electron microscopy, Fourier transform infrared spectroscopy and electrochemical impedance spectroscopy were carried out to characterize the film which exhibits excellent electrocatalytic activity toward the oxidation of p-Hyd. Based on optimum conditions, the oxidation peak of p-Hyd 0.91V（vs SCE） current is linearly related to the concentration of p-Hyd in the range from 1 to 160 μM with the detection limits of 0.15 μM（S/N = 3）. This modified electrode displays good reproducibility and selectivity for the determination of p-Hyd.