Polishing the electrode surface

Ethanol (2-200) x 10 5M Ethanol 5.3 x 10 6M RSD = 8.3% in = 10, after polishing the electrode surface) RSD = 6.5% in = 9, different biosensors) The useful lifetime of a single AOD-HRP-ferrocene composite electrode was of approximately 15 days with no need of enzyme stabilisers in the electrode matrix. Both batch and FIA modes. 

The electrode material has also been found to influence the surface morphology of electrochemically prepared PPy films. In our own work, we used transmission electron microscopy (TEM) to investigate the cross-sectional structure of PPy films prepared on different substrates.165 In all cases, the large surface globules were observed to be the caps of cone-shaped structures that extended to the electrode surface of the PPy him (see Chapter 3). Interestingly, Yoon and coworkers showed that the cauliflower-type surface morphology could be virtually eliminated by carefully polishing the electrode surface.152... 

Once the resin is hardened, polish the electrode surface, which is wet with doubly distilled water and then smooth thoroughly, first with abrasive paper of different grades of and then with alumina paper (polishing strips 301044-001, from Orion, Spain) (reeNote 1). 

Before measurements, the electrode was polished chemically with Cr(>, according to the procedure described in Ref. 12. After polishing, the electrode surface was soaked in concentrated sulfuric acid for about 20 min and then rinsed thoroughly with water. 

A special example of a passive metal is iron. The primary oxide film on polycrystalline and pure iron (dry air, 20 °C) has a thickness of about 5 nm and is soluble in acid and neutral media. In strong nitric acid, an oxidizing medium, the usual dissolution of iron in acids is blocked by the formation of a passive film. In other acids this film can only be formed, if an anodic potential is applied. Polishing the electrode surface facilitates the formation of the passive film. 

Electrochemically polished and chemically treated Cd(0001), Cd(10T0)t Cd(l 120), Cd(lOTl), and Cd(ll2l) electrodes have been studied by impedance and cychc voltammetry by Lust et al.152 153 249 664 665 a slight variation of capacitance (3 to 6%) has been observed with v. In the case of chemically treated electrodes, a somewhat higher (5 to 10%) dependence of C on v has been explained by the geometric roughness of the electrode surface. 

The study of metal ion/metal(s) interfaces has been limited because of the excessive adsorption of the reactants and impurities at the electrode surface and due to the inseparability of the faradaic and nonfaradaic impedances. For obtaining reproducible results with solid electrodes, the important factors to be considered are the fabrication, the smoothness of the surface (by polishing), and the pretreatment of the electrodes, the treatment of the solution with activated charcoal, the use of an inert atmosphere, and the constancy of the equilibrium potential for the duration of the experiment. It is appropriate to deal with some of these details from a practical point of view. 

The mechanical electrochemishy equipment is different from conventional electrochemistry equipment, which can exert pressure to the surface of the electrode by adjusting die height of the lifting platform and change the pressure of electrode (see Fig. 8.1). Before the experiment, the electrode surface was polished, and the grinding media, electrolyte and reagent were added in order. 

Moreover, the oxidation process is strongly dependent on the state of the electrode surface. At a freshly cleaned and polished lead the oxidation of 5b occurs at p/2 = — 1.52 V on the first sweep, but on subsequent cycles the potential shifts in the cathodic direction approaching E j2 = —1.72 V. 

Figure 17-12 (a) Rotating disk electrode. Only the polished bottom surface of the electrode, which is typically 5 mm in diameter, contacts the solution, (b) Schematic concentration profile of analyte near the surface of the rotating disk electrode when the potential is great enough to reduce the concentration of analyte to 0 at the electrode surface. 

Whether the GC is mounted or not, the most common polishing procedure involves a series of abrasives used as slurries on a commercial fabric polishing cloth. The as-received electrode or GC piece is first sanded on 600 grit emery paper to remove gross surface defects and impurities. In most cases, each polishing step involves a circular motion for a few minutes, with the objective being uniform roughness over the electrode surface. The sandpaper is followed by... 

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