Response of fluorescein to carbon dioxide in dimethyl sulfoxide–water mixtures

Abstract

The response of Fluorescein (FL) dye and potassium hydroxide to gaseous CO₂ in a solution of dimethyl sulfoxide (DMSO)–water has been investigated. A general equation [H⁺]=α[CO₂]^β(where α and β are constants) is derived to explain the reactions of these solutions with CO₂; β < 1 in a non-aqueous or non-aqueous–aqueous solution of base and β= 1 in an aqueous solution of base. Increasing the mole fraction of H₂O, x, in an FL–KOH–DMSO–H₂O mixture (with x= 0.0–0.63) can enhance the sensitivity of the dye–solvent solution to CO₂ but with x= 0.63–1.00, the sensitivity decreases. As the concentration of KOH in FL–KOH–DMSO solution is increased, the sensitivity of this solution to CO₂ decreases.