A sequential injection method for the determination of tween-80 in natural water samples using a fluorescence enhancement of the dye eosin-B

A simple sequential injection (SI) method is reported for the determination of the non-ionic surfactant polyoxyethylene sorbitan monoleate (Tween-80). The proposed method is based on a fluorescence enhancement of the probe 4',5'-dibromo-2',7'-dinitro fluorescein, disodium salt (Eosin B) in the presence of a surfactant. The procedure is optimized using the univariate method of optimization. The optimum operating conditions are as follows: reagent concentration, 40 ppm; pH, 4.5; aspirated volumes of sample and reagent, 120 muL and 100 muL, respectively. With the optimum conditions described, linear calibration curves were obtained from 10 - 200 ppm. The detection limit was 1.7 ppm and the maximum relative standard deviation of the method was 2.7% (n = 5). The fluorescence excitation and emission were fixed at lambda(ex) = 545 nm and lambda(em) = 585 run. The method was successfully applied to the determination of (TW-80) in natural water samples.