Development of a Cr(III)-specific potentiometric sensor using Aurin tricarboxylic acid modified silica

A new chelating resin, Aurin tricarboxylic acid modified silica, was synthesized. The resin behaves as a selective chelating ion exchanger for Cr(III) at a pH 3.8-5.5. A polyvinyl chloride-based membrane electrode of the modified silica has been fabricated and explored as sensor for Cr(III) ions. The membrane works well over the concentration range 7.0 × 10⁻⁶ to 1 × 10⁻¹ M of Cr(III) with a Nernstian slope of 19.0 mV per decade of concentration. The response time of the sensor is 10 s and it can be used for a period of 5 months. The performance of the sensor is best in the pH range 3.5-6.5 and it also works well in partially non-aqueous medium. The selectivity coefficient values depicts that the membrane exhibits good selectivity over a number of interfering ions. Moreover, the membrane sensor has been applied to analyse the concentration of chromium in certified steel sample and food materials with greater than 97% accuracy.