Chemically Modified Electrodes In Pharmaceutical Analysis

Electrochemical method, as a novel and highly sensitive analytical technique for medicine analysis, performed some good characteristic, such as fast analytical speed, simple instrumentation and low cost. Chemically modified electrode is investigated very actively in the current research field of electroanalytical chemistry, and its application is very extensive. Recently, the application of chemical modified electrode in the pharmaceuticals analysis in recent years has been made great progress. In this work, the modified electrodes by carbon nanotubes and polymer film were applied to the determination of some drug molecules. The major contents arre described as follows:Part 1.Determination of ethamsylate at the multi-wall carbon nanotubes modified glassy carbon electrode in the presence of CTABA multi-wall carbon nanotubes (MCWNTs) film coated glassy carbon electrode (GCE) was fabricated, and the electrochemical behavior of ethamsylate on the MWCNTs/GCE was investigated. The anodic peak current of ethamsylate increased significantly and the its peak potential shifted negatively at MWCNTs/GCE compared to that at bare GCE. This indicated that MCWNTs featured highly effective catalysis to the electrochemical oxidation of ethamsylate. And the addition of surfactant cetyltrimethylammonium bromide (CTAB) can further enhance anodic peak current of ethamsylate. On optimal conditions, a good linear relationship between anodic peak current and ethamsylate concentration was obtained in the range of 5.0×10-8 ~ 1.0×10-5 M with the detection limit of 2.0×10-8 M (S/N = 3). The responses of repeated measurements at the identical and the renewed surface of the MWCNTs/GCE were examined with relative standard deviation of 2.6% (n=30) and 3.5% (n=10), respectively, indicating that the chemically modified electrode showed excellent reproducibility. The proposed method has been used to determine ethamsylate concentration in biological fluids with satisfactory results.Part 2.Determination of dobutamine at poly (Alizarin Red) Film Modified ElectrodesThe electrochemical behavior of dobutamine in poly(alizarin red) film modified electrodes(PAR/GCE) have been studied by cyclic voltammetry. The experiments showed the good effect of accumulation on dobutamine in this modified electrode. On optimal conditions, a good linear relationship between anodic peak current and dobutamine concentration was obtained in the range of 5.0×10-8 ~ 7.0×10-5 mol/L with the detection limit of 1.5×10-8 M (S/N = 3) by differential pulse voltammetry. The responses of repeated measurements at the identical and the remodified surface of the PAR/GCE were examined with relative standard deviation of 3.2% (n=40) and 3.7% (n=10), respectively, indicating that the chemically modified electrode showed excellent reproducibility. The proposed method has been used to determine dobutamine concentration in serum and dobutamine injectiin samples with satisfactory results.Part 3 . Electrocatalytic oxidation of isoniazid and its trace measurement at glassy carbon electrode modified with poly(Amidsulfonic Acid)A novel chemically modified glassy carbon electrode modified with poly(amidsulfonic acid) (denote as PAA-GCE) by electropolymerization, and the electrochemical behavior of isoniazid at PAA-GCE was investigated. The anodic peak current of isoniazid increased significantly and peak position shifted negatively for about 40 mV at PAA-GCE compared to that at bare GCE. This indicated that poly(amidsulfonic acid) performed effective catalysis to the electrochemical oxidation of isoniazid. Under optimal conditions, a good linear relationship between anodic peak current and isoniazid concentration was obtained in the range of 5.0×10-8 ~1.0×10-5 M with the detection limit of 1.0×10-8 M (S/N=3). The responses of repeated measurements at the identical and the renewed surface of the PAA-GCE were examined with relative standard deviation of 3.7 % (n=25) and 4.7% (n=10), respectively, indicating that the chemically modified electrode showed good reproducibility. The proposed method has been used to determine isoniazid concentration in injection and tablet samples with satisfactory results.