Chromium(III) porphyrin as a selective ionophore in a salicylate-selective membrane electrode

The construction, potentiometric response properties, and applications of a novel ion-selective electrode with high selectivity toward salicylate are described. Chromium(III) tetraphenylporphyrin chloride was used as ion carrier into plasticized PVC membrane. This ionophore is capable of serving as both a positively charged and neutral carrier, depending on the pH of the sample solution. The influence of several variables was investigated to optimize the potentiometric response and selectivity of the electrode. The resulting electrode demonstrates a near-Nernstian response over a wide range of salicylate concentration (10(-6)-10(-1) M). This electrode has a fast response time and micromolar detection limit and could be used over a wide pH range (3-9). The proposed electrode showed very high selectivity for salicylate over a number of common inorganic and organic anions. The specific interaction of salicylate with the central metal of porphyrin is described based on UV-visible absorption spectra. The electrode was successfully applied to the determination of salicylate in pharmaceutical preparations and clinical samples.