A continuous flow system combined with a sensing fluorimetric transductor for the determination of β-naphthol

A single automatic method for continuous flow determination of beta-naphthol based on the enhancement of its native fluorescence once the analyte was transitorily retained on-line on a solid support (QAE A-25 resin) is reported So, a flow-through optosensor was developed using a flow-injection analysis system with solid phase fluorimetric transduction. KCl (0.15 mol l(-1)) at pH 12.0 was used as carrier solution. To obtain the optimum fluorescence signal the wavelengths chosen were 245 nm (excitation) and 420 nm (emission). The response of the sensor was directly proportional to the sample volume injected in the studied range 40-1500 mul. Approximately one higher order of magnitude is achieved in sensitivity when 1500 mul are used with respect to the use of 40 mul of sample. The sensor was calibrated for three different injection volumes: 40, 600 and 1500 mul, responding linearly in the measuring range of 2-60, 0.5-15 and 0.2-5 mug l(-1) with detection limits of 0.5, 0.09 and 0.05 mug l(-1), respectively. The relative standard deviation for ten independent determination is 0.6% (40 mul), 0.9% (600 mul) and 2.3% (1500 mul). A recovery study was performed onto three different spiked water samples at concentration levels from 1 to 2.5 mug l(-1) and the recovery percentage from the experimental data ranged between 101 +/- 2 and 105 +/- 5. (C) 2002 Elsevier Science B.V. All rights reserved.