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.

Development of Capillary Zone Electrophoresis Method for the Simultaneous Separation and Quantification of Metformin and Pioglitazone in Dosage Forms; and Comparison with HPLC Method

“…The method of least squares was used and, accordingly, the regression parameters were calculated. As a result, the correlation coefficients for MET and PIO were 0.9988 and 0.9985 respectively, indicating acceptable linearity [ 41 , 42 ]. The obtained values of the slope for MET and PIO were 0.0103 and 0.0388, respectively, indicating acceptable sensitivity as well.…”

“…The standard deviations (SD) of the slopes for MET and PIO were 0.00028 and 0.00122, respectively. Low standard deviation values compared with the slope values of both drugs show low uncertainty in the regression analysis that may arise from the effect of indeterminate errors on the slopes [ 41 , 42 ]. The y-intercept values for MET and PIO calibrations were +0.0164 and −0.1603, respectively.…”

“…Despite MET calibration recorded positive intercept, the small value suggests low level of the existence of interference with the response or low level of the saturation of responses at high concentrations. Similarly, the negative y-intercept of PIO at a small value enhances the claim of satisfactory sensitivity [ 41 , 42 ]. Furthermore, the standard deviation values of the y-intercepts for MET and PIO were 0.0140 and 0.0069, respectively.…”

“…Furthermore, the standard deviation values of the y-intercepts for MET and PIO were 0.0140 and 0.0069, respectively. Low levels of standard deviations of both drugs indicate low level of uncertainty of calibrations [ 41 , 42 ]. Nevertheless, the uncertainty of MET is, to some extent, higher than that of PIO.…”

“…Nevertheless, the uncertainty of MET is, to some extent, higher than that of PIO. Additionally, the standard error of the estimate values, or in another context the standard deviation of the regression, for MET and PIO were 0.01626 and 0.0876 for, respectively, indicating closer points to the calibration curve [ 41 , 42 ].…”