Paraffin-impregnated graphite

Three-phase electrodes have been constracted in two major configurations. Most frequently, it consists of a paraffin-impregnated graphite electrode (GE) modified with a macroscopic droplet of a water immiscible organic solvent (O) (e.g., nitroben-... 

These drawbacks can be avoided to a large extent, using the voltammetry of microparticles—a technique involving solid state electrochemistry where down to about 10 to 10 mol of sample [74-78] can be transferred by abrasion into the surface of an inert electrode, usually paraffin-impregnated graphite electrodes, and the electrode is later immersed in a suitable electrolyte for recording its voltam-metric response. The response of this sample-modified electrode, consisting of the reduction or oxidation of the solid materials, becomes phase-characteristic. 

As shown in Fig. 2.5, the cyclic voltammograms for Prussian blue attached to paraffin-impregnated graphite electrodes (PIGEs) in contact with aqueous electrolytes exhibit two well-defined one-electron couples. Prussian blue crystals possess a cubic structure, with carbon-coordinated Fe + ions and nitrogen-coordinated Fe + ions, in which potassium ions, and eventually some Fe + ions, are placed in the holes of the cubes as interstitial ions. The redox couple at more positive potentials can be described as a solid-state process involving the oxidation of Fe + ions. Charge conservation requires the parallel expulsion of K+ ions [77] ... 

Fig. 2.21 Square wave voltammograms for alizarin-modified paraffin-impregnated graphite electrodes immersed into 0.50 M potassium phosphate buffer (pH 7.0) (a) before, and (b) after application of a potential step of —1.50 V during 15 min. Potential initiated at —0.85 V in the positive direction. Potential step increment 4 mV square wave amplitude 25 mV frequency 5 Hz...

Fig. 3.11 Tafel plots for verdigris (A), atacamite (B), paratacamite (C), and cuprite (D) from linear scan voltammograms at sample-modified, paraffin-impregnated graphite electrodes immersed in 0.50 M potassium phosphate buffer (pH 7.0). Potential scan rate 50 mV/s...

An example of the application of Tafel analysis is provided by samples taken for a bronze montefortino helmet from the Gabriel river valley (Kelin and Ikalesken period) in the Valencian region of Requena, dated back to the Second Iron Age (see Fig. 3.13). Upon attachment to paraffin-impregnated graphite electrodes immersed in 0.50 M phosphate buffer, voltammetric signals such as depicted in Fig. 3.14 were found [183]. 

Fig. 4.5 Square-wave voltammograms for commercial Brazilwood (a) and logwood (e), and mixtures of both pigments containing 50% (b), 75% (c), and 85 % (w/w) (d) of Brazilwood, attached to paraffin-impregnated graphite electrodes. Electrolyte ...

Domenech A, Domenech-Carbo MT, Sauri MC (2005) Electrochemical identification of flavonoid dyes in work of art samples by abrasive voltammetry at paraffin-impregnated graphite electrodes. Talanta 66 769-782. 

Komorsky-Loviic S, Loviic M, Bond AM (1992) Comparison of the square-wave stripping voltammetry of lead and mercury following their electrochemical or abrasive deposition onto a paraffin impregnated graphite electrode. Anal Chim Acta 258 299-305. 

Paraffin impregnated graphite See -> paraffin impregnated graphite electrode. 

Paraffin impregnated graphite electrode (PIGE) - electrode prepared from graphite rods by impregnation with melted paraffin under vacuum. These electrodes are not permeated by aqueous solutions and can be used for solution studies, as well as for immobilizing microparticles and microdroplets to study their electrochemistry. See also - carbon, - voltammetry of immobilized microparticles. 

FIGURE 2.7 SQWV for microparticulate deposit of PY ion attached to zeolite Y deposited on paraffin-impregnated graphite electrode in contact with 0.10 M Et NClO /MeCN. Potential step increment, 4 mV square-wave amplitude, 25 mV frequency. 5 Hz. 

FIGURE 4.4 CAs for TPY+ Y-modified paraffin-impregnated graphite electrodes in contact with 0.10 M solutions of (from upper to helow) liCNPIy, liu.,NPI, and I lex.,NPly, in MeCN. Applied potential, -0.35 V vs. AgCl/Ag. 

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