Utilization of 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) as a fluorogenic reagent for the development of a spectrofluorometric assay method for taurine in energy drinks

Abstract

The development of a simple, inexpensive, sensitive, and selective spectrofluorometric assay method for taurine in energy drinks utilizing 4-fluoro-7-nitro-2,1,3-benzoxadiazole as a fluorogenic agent is described. Conditions affecting the derivatization reaction are investigated and optimized. The optimal conditions are found to be as follows: buffer, pH 10; 4-fluoro-7-nitro-2,1,3-benzoxadiazoleconcentration, 0.05%; reaction time, 30 min; temperature, 50 °C. Fluorescence measurements are carried out at a wavelength of 542 nm, with excitation at a wavelength of 485 nm. The method is validated under the optimum conditions. The method is found to be linear in the range of 2.0–12.5 µg/mL, with a correlation coefficient of 0.9993. The limits of detection and quantification (µg/mL) are 0.6 and 2.02, respectively, which are appropriate for taurine assays in commercial energy drinks. In addition, the proposed method recorded excellent accuracy since the recovery values caused by presence of excipients are found to be in the range of 99.3%–102.87%. The values of relative standard deviation for intra- and inter-day precision were found to be in the ranges of 0.236%–0.659% and 2.12%–2.63%, respectively.