Platinum Electrode stationary

Fig. 9. Sampled-current voltammograms recorded at a stationary platinum electrode in the 66.7 m/o AICI3-EtMelmCl melt. The Ag(I) concentrations were ( ) 5.0, (A) 10.0, ( ) 15.0, (T) 20.0, and ( ) 25.0 mmol L-1. The current was sampled at 10 s. Adapted from Zhu et al. [89] by permission of The Electrochemical Society.

Anionic and Cationic Carbonyls. The polarographic behaviour of Et N-[Fe(CO)3NO] at dropping mercury and stationary platinum electrodes has been studied. Two anodic waves and one cathodic wave were observed and the following reactions were suggested ... 

Some understanding of liquid flow along a solid-solution interface is useful in understanding these techniques. Consider a stationary platinum electrode immersed in a stirred solution. Three regions of solution flow can be identified. 

By HPLC analysis, 1.4 X lO" M oxalic acid and 1.3 X10" M oxamic acid were found in the solution containing 10 % ammonimn carbonate and 0.1 M MgCl2 after irradiation for 100 hrs at 90 °C. The voltammetric determination of oxalic and oxamic acids based on oxidation waves at a stationary platinum electrode supported the the HPLC result. 

Figure 23-24 shows the current response when a solution that is 6 mM in K3Fe(CN)6 and 1 M in KNO3 is subjected to the cyclic excitation signal shown in Figure 23-23. The working electrode was a carefully polished stationary platinum electrode, and the reference electrode was a saturated calomel electrode. At the initial potential of +0.8 V, a tiny anodic current is observed, which immediately...

BZ was al so partially oxidized by Ag(II) in a small H-cell with stationary platinum electrodes. Compounds identified in anolyte extracts included phenol, hydroquinone, benzoquinone, benzaldehyde, benzoic acid, methyl benzoate, benzonitrile, benzonitrile aldehyde, and 4-nitro butylnitrile. The yellow color of the anolyte was probably due to benzoquinone, which had a relatively high concentration. A compound which was tentatively identified as benzoquinone epoxide ( 11403) was present at the highest concentration and is believed to be a product of the oxidation of benzoquinone. Numerous nitrated aromatics were also detected and include nitrobenzene, dinitrobenzene isomers, nitrophenol isomers, and dinitnophenol isomers. Intermediates are summarized in Table 3 and classified as I. BZ substrate II. nitrated BZs HI. phenols, quinones, and epoxides IV. nitrated phenols V. BZ substituted with aliphatic and aromatic... 

Propiomazine hydrochloride exhibits an anodic wave at +0.8v in acidic aqueous solution at a concentration range of 10 - to 10 5k using a stationary platinum electrode vs. a calomel reference electrode, suitable for a quantitative assay O. The wave corresponds to the oxidation of the stilfur in the phenothiazine nucleus to the sulfoxide l. 

The anodic waves of dialkylsulphides, obtained with a stationary platinum electrode, do not look very promising from the anal5itical point of view, owing to the properties of the stationary solid electrodes and to the peak-shaped form of the resulting currents. An indirect method is therefore now being investigated in our laboratory. 

From the experimental point of view, for reductions, DC-polarography at the dropping mercury electrode (DME) or cyclic voltammetry (CV) at the hanging mercury drop electrode (HMDE) were used and for controlled-potential electrolyses at negative potentials, a mercury pool electrode was employed. For both oxidative and reductive experiments, voltammetry at the platinum rotating disk electrode (RDE) and CV at the stationary platinum electrode were applied. All experiments were performed in a three-electrode system with a platinum counter electrode. For measurements in analytical scale (a standard aminocarbene concentration was 3x 10-" mol/1), an undivided cell for 5-10 ml was used and for preparative electrolyses a two-compartment cell of the H-type was employed [14]. The potentials were referred to the saturated calomel electrode (SCE), which was separated from the investigated solution by a double-frit bridge. 

Figure 9. Chronoamperometric curves for the growth of a polythiophene film on a stationary platinum disk electrode, from 0.1 M thiophene and 0.1 M LiC104 acetonitrile solutions, at different water contents (---) 0.04%, (--------) 0.14%,...

Two identical stationary micro-electrodes (usually platinum) across which a potential of 0.01-0.1 V is applied can be used in place of either the DME or the rotating platinum micro-electrode. The equivalence point is marked by a sudden rise in current from zero, a decrease to zero, or a minimum at or near zero (Figures 6.16(a), (b) and (c)). The shape of the curve depends on the reversibility of the redox reactions involved. The two platinum electrodes assume the roles of anode and cathode, and in all cases a current flows in the cell only if there is a significant concentration of both the oxidized and reduced forms of one of the reactants. In general, two types of system can be envisaged ... 

Figure 6.17 A Randles-SevCik plot of 7p against Data refer to the oxidation of aqueous ferrous ion at a stationary platinum wire electrode. The non-linearity at the higher scan rates represents the demand for flux at the working electrode being too great since i is too fast, while the non-zero intercept is caused by non-faradaic currents contributing...

It is further important to note that all the current/voltage characteristics depicted in Fig. 6 are unchanged by the presence of liquid fuels such as methanol, formaldehyde, formic acid, or hydrazine. The phthalocyanine electrode remains completely inert toward such substances. For this reason, no mixed potential can be formed at a phthalocyanine electrode, as for example can occur at a platinum electrode, when it is used as cathode in a methanol cell containing sulfuric acid. This is shown by a comparison (see Fig. 7) of the stationary characteristics of the platinum alloy we found to be the most active in the presence of methanol, namely a Raney ruthenium—rhodium electrode, with an iron phthalocyanine electrode, both measured in 4.5 N H2SO4+2M CH3OH. 

Flow electrodes. Rather than move the electrode past the solution, the sample solution can be flowed past a stationary electrode. The tubular platinum electrode (Figure 5.34) and the gold micromesh flow-through electrode (Figure 5.35) are both ingenious attempts to produce electrodes that are useful for the measurement of electroactive materials in a continuously flowing stream. Ap-... 

Capillary electrophoresis separations are dependent on the relative mobilities of analytes under the influence of an electric field and do not depend on mobile phase/stationary phase interactions. A fused silica capillary is filled with a buffer and both ends submerged into two reservoirs of the buffer. A platinum electrode is immersed in each reservoir and a potential difference (5-30 kV) is applied across the electrode. An aliquot of sample of a few nanoliters is injected onto the capillary by either hydrostatic or electrokinetic injection, and the components migrate to the negative electrode. Separations of analytes arise from differences in the electrophoretic mobilities, which are dependent on the mass-to-charge ratio of the components, physical size of the analyte, and buffer/analyte interactions. An electro-osmotic flow (EOF) of the buffer occurs in the capillary and arises as a result of interactions of the buffer with dissociated functional groups on the surface of the capillary. Positive ions from the buffer solution are attracted to negative ions... 

Figure 10.2 Oxidation of molecular hydrogen dissolved in 0.1 M HCIO4 at a stationary gold electrode modified by 0.1 mg cm of platinum dispersed in different electron conducting polymers sweep rate = 5 mV s T = 25°C (—) polyaniline (---) polypyrrole (—) poly(3-methylthiophcnc) (...) pyrrole-dithiopene copolymer, (Reprinted with permission from ref 133)...

Fig. 6.8 Copper powder particles obtained at different overpotentials from 0.10 M CUSO4 in 0.50 M H2SO4 onto stationary platinum wire electrodes painted with shellac. Deposititm time 15 min. Overpotentials of electrodeposition (a) 500 mV, (b) 600 mV, and (c) 700 mV (Reprinted from Ref. [5] with kind permission from Springer)...

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