A FIBEROPTIC FLUORESCING SENSOR FOR AMINE VAPORS

A fibre-optic fluorescing sensor based on a film of the pH-sensitive molecule 2-naphthol, hydrogen-bonded to a matrix of poly(ethylene oxide), is described. The indicator molecule has well-defined fluorescence peaks, due to protonated and deprotonated forms, and the relative proportions of these change in response to interaction with amine vapours. No significant quenching by oxygen is apparent and water vapour does not influence the behaviour below a relative humidity of 90%. At higher humidities the effect is pronounced. The lower limit for reliable detection of monoethanolamine (MEA), and several other amines, is better than 1-mu-M (24 ppm). The sensor responds reversibly and the time taken to achieve 90% of full-scale variation is approximately 45 s. Recovery to 90% of initial response takes around 5 min.