Analytical Sciences

A Sequential Injection Method for the Determination of Tween-80 in Natural Water Samples Using a Fluorescence Enhancement of the Dye Eosin-B

Salma M. Z. AL-KINDY,*  Fakhr Eldin O. SULIMAN,* Salama B. SALAMA,* Mohamed AOUDIA,* Seif N. AL-BAHRY,** and Hamoud S. AL-BAHLANY**

*Department of Chemistry, College of Science, Sultan Qaboos University, Box 36, Al-Khod 123, Sultanate of Oman
**Department of Biology, College of Science, Sultan Qaboos University, Box 36, Al-Khod 123, Sultanate of Oman

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 µL and 100 µL, 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 λ_ex = 545 nm and λ_em = 585 nm. The method was successfully applied to the determination of (TW-80) in natural water samples.

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