Zirconium Compound Modified Carbon Paste Electrode Applied In Pharmaceutical Analysis

Carbon paste electrode（CPE） is composed of graphite powder and binder. It is prepared by squeezed carbon paste into electrode tube. CPE has a great deal of specific advantages such as low residual current, simple preparation, non-toxic, large potential window, high conductivity, long lifetime. Moreover, the surface of electrode is easily polishable and renewable. Therefore, CPE plays an important role in electrochemical analysis. But for now, the application of bare CPE is limited. In order to improve its performance, it need to be chemical modified.The main work of this paper is to prepare sensitive voltammetric sensorchemical modified carbon paste electrode, for the sensitive and rapid determination of drug molecules. The content mainly included the following three aspect:1. Preparation of ZrO₂ nanoparticles was complex. While, Zirconia films could be deposited onto gold substrate from ZrOCl₂ aqueous solution using cyclic voltammetry（CV）. Thus, combining the preparation of CPE, ZrOCl₂ was doped into carbon paste and then was electrochemically treated. We speculate that ZrOCl₂ was transferred to ZrO₂ on the electrode surface. The electrode was designed as ET-ZrOCl₂-CPE（electrochemically treated ZrOCl₂ doped carbon paste electrode）. The preparation of this electrode was simple. If necessary, pushing excess paste out of the tube and polishing with weighing paper until a shiny surface was obtained. A brand new surface was obtained in this way. The surface morphology and electrochemical properties of the electrode were investigated by scanning electron microscopy and cyclic voltammetry. The electrochemical behavior of daidzein at this electrode was investigated in detail and the kinetics parameters were calculated. Under the optimized conditions, the response currents were linear relationship with daidzein concentrations in the range of 3.0×10-8 to 2.0×10-6 mol L-1 with a detection limit of 1.0×10-8 mol L-1 in phosphate buffer solution with pH 2.5.2. In the first system, the number of nanopaticles was decreased after the electrochemical treatment. This indicated that some ZrOCl₂ or the product fell off during the electrochemical treatment process. Therefore, we introduced β-CD to improve the stability of functional materials with its special structure. We incorporated ZrOCl₂ and β-CD into graphite powder followed with an electrochemical treatment process. This sensor exhibited remarkable enhancement response towards ligustrazine（TMPZ） compared with other related electrodes. The reaction mechanism of TMPZ was investigated and an analytical method was established for the sensitive determination of TMPZ on this sensor. The proposed electrode was applied to quantitative analysis of TMPZ in real samples with satisfactory results.3. To introduce graphene materials with specific surface area and good electrical conductivity, and improve the stability of ZrO₂ nanoparticles on the electrode surface, we prepared Zr O₂/graphene（ZrO₂/Gr） nanocomposites. High uniform Zr O₂ nanoparticles were deposited on Gr sheet. By introducing this nanocomposite into carbon paste electrode, the specific surface area and conductivity was largely increased. The obtained electrochemical sensor showed sensitive response for troxerutin. Based on this sensor, an accurate sensitive analytical method for troxerutin was established with a linear range from 2.0×10-9 to 3.0×10-7 mol L-1 and a detection limit 6.0×10-10 mol L-1. Meanwhile, the electrochemical properties of troxerutin were investigated in detail. This proposed method was applied in the determination of troxerutin in real samples with satisfactory results.