Electrode paraffin-impregnated graphite PIGE

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] ... 

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. 

The hardness of an electrode often limits the ability of a solid compound to adhere to an electrode surface. For example, fairly soft, flake-like materials, such as many organic compounds, will preferably adhere to a hard surface, e.g., that of a glassy carbon (GC) electrode, while hard solids such as oxides or minerals will adhere to a soft surface such as that of a paraffin-impregnated graphite electrode (PIGE). 

Fig. 4.8a-c Consecutive cyclic voltammetric curves obtained for 3-methylthiophene droplets attached to a paraffin-impregnated graphite electrode in the presence of an aqueous solution containing 0.5 moldm LiC104. Cycles a 1 to 4 (curves 2-5) b 5-14 c 15-24 and 25-34. Curve 7 shows the background current ofthe uncoated PIGE. Scan rate 100 mVs . (Reproduced from [131] with the permission of Elsevier Ltd.)... 

---