Wire coating, poly , effect

Effect of Poly(vinyl chloride) Wire Coating... 

A potentiometric determination of saccharin was proposed by Fatibello-Filho et al. [86]. In this method, saccharin was potentiometrically measured using a silver wire coated with a mercury film as the working electrode. With this, the main difficulty was the presence of a precipitate (mercurous saccharinate) that could adsorb on tube walls and the electrode surface. To avoid these undesirable effects, a relocatable filter unit was placed before the flow-through potentiometric cell and a surfactant was added to the carrier solution (Figure 24.12). The same investigation team reported the construction and analytical evaluation of a tubular ion-selective electrode coated with an ion pair formed between saccharinate anion and toluidine blue O cation incorporated on a poly(vinyl chloride) matrix [87]. This electrode was constructed and adapted in a FIA system. The optimum experimental conditions found were an analytical path of 120 cm, an injection sample volume of 500 pL, a pH of 2.5, a flow rate of 2.3 mL/min, and a tubular electrode length of 2.5 cm. 

A cell with a small Pt disk working electrode coated with a polyelectrolyte multilayer made of poly(allylamine)-poly(vinyl sulfate), a Pt wire counterelectrode and a reference SCSE may be used for selective amperometric determination of H2O2, in the presence of ascorbic acid (22), uric acid (29) and acetaminophen (148). The latter three compounds show a significant response with the bare working electrode at +0.6 V while a practically nil one with the coated electrode. The reason for this selectivity may be an exclusion effect by the coating. ... 

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