Chromogenic and Fluorogenic Reactands: New Indicator Dyes for Monitoring Amines, Alcohols and Aldehydes

Abstract

In the past few years a wide range of optical sensors for ions has been presented. Sensors for pH are based on the protonation/deprotonation of pH indicator dyes [1] and sensors for cations and anions use a combination of pH indicator dyes with selective ionophores (via the mechanisms of coextraction or ion-exchange) [2]. In the case of coextraction and ion-exchange, the uncoloured ionophore recognizes the analyte while the pH indicator dye changes its colour [2]. This approach is highly cross-sensitive to pH and has not found practical application so far. A more sophisticated and synthetically challenging approach is to use selective fluoro- and chromoionophores [1,3,4]. They are advantageous because the dyes both selectively recognize the analyte and simultaneously change their colour. Fluoroionophores for sodium and potassium with very low cross-sensitivity to pH can be found in the AVL OPTI devices [5]. Fig.1 Principle of analyte recognition using fluorogenic ligands and reactands. Apart from an increase in fluorescence upon interaction with the analyte, changes in absorbance can be observed as well