Optode sensor for on-site detection and quantification of hydroxide ions in highly concentrated alkali solutions

Abstract

A colorimetric strip sensor has been developed for selective visual detection and quantification of hydroxide ions in a highly concentrated alkali solutions. The sensor was made by immobilizing the 4,4-bis-[3-(4-nitrophenyl) thiourea]diphenyl ether derivative of thiourea in a Whatman 541 filter paper. Immobilization of the derivative was optimized with respect to its concentration, stability and uniformity in the solid substrate. The sensor strip on reaction with hydroxide ions turns orange in color, and the intensity of the color was found to be proportional to the concentration of hydroxide ions. Developed strip sensor exhibits a wide linear dynamic range of 0.5 M to 8 M and a response time within 5 min. The adequate reproducibility as well as reusability of the strip sensor is suitable for a rapid on-site quantification of hydroxide ions in concentrated alkaline media. Developed strip sensor was successfully applied for the determination of hydroxide concentration in nuclear fuel decladding solutions.