Awm. Lee et al., REVERSE-PHASE OPTODE - DESIGN AND CHARACTERIZATION OF AN ORGANIC ACID-SELECTIVE OPTODE MEMBRANE-BASED ON FLUORESCEIN SODIUM, Analytica chimica acta, 322(1-2), 1996, pp. 99-105
Hydrophilic gelatin membranes incorporating water soluble fluorescein
sodium immobilized at the tip of an optical fiber were developed as th
e first 'reverse-phase' optode membrane system for the determination o
f organic acids as exemplified by benzoic acid. In contrast to the tra
ditional optode membrane application, the fluorescence detection of or
ganic acids by the present system was carried out in an organic medium
(hexane). Under experimental conditions, the optical fiber coated mem
brane exhibited a linear response in the range 4.72 x 10(-4)-4.72 x 10
(-2) mol l(-1) benzoic acid hexane solution with a slope of 0.2 relati
ve fluorescent intensity units per concentration decade. The selectivi
ty, response time, reproducibility and lifetime of this optical device
are discussed.