Flow injection analysis of water vapour based on a fluorosensor

A new fluorimetric sensor incorporated with flow injection (FI) technique has been developed for water vapour quantification. The sensor was fabricated by immobilising rhodamine 6G in an organogel deposited on an overhead transparency film. The organogel was prepared from a solution of gelatine, rhodamine 6G and sodium bis(2-ethylhexyl)sulphosuccinate (AOT) in water-isooctane. Isooctane was employed as the organic solvent and AOT as the surfactant, thus forming water-in-oil microemulsions with a high capacity for water solubilisation. The organogel-based optode membrane showed a strong fluorescence at 564nm when it was excited at 540nm. The fluorescence intensity of the optode membrane at 564nm decreased upon exposure to water vapour. The sensing system exhibited a relatively wide linear dynamic range from 0.252 to 2.52kPa water vapour pressure and also demonstrated a good linearity (correlation coefficient was 0.9912) at 20.0°C and 1atm pressure. The sensor had good repeatability, photostability and long-term stability. Oxygen, carbon dioxide gases, acetone, toluene, ethanol, chloroform, acetic acid vapours and NO(x) did not cause any interference. The addition of AOT to the organogel was shown to enhance the sensitivity for the detection of water vapour and also shortened the exposure and recovery times in which 1cycle of FI was completed within 1min. Copyright (C) 2000 Elsevier Science B.V.