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A simple, fast, and ecofriendly spectrofluorometric method was developed and validated for determination of mono sodium glutamate (MSG). The method depended on the reaction between MSG and iron (III) salicylate based on ligand exchange mechanism. Addition of MSG turned-on the fluorescent response of iron (III) salicylate at λem 411 nm. Reaction conditions including reagent concentration, pH, and time were optimized. The method was validated regarding the ICH guidelines. The method determined MSG within the linearity range of 25—250 µM with a coefficient of determination of 0.9967 and a calculated limit of detection of 1.73 µM. Furthermore, the developed method was successfully applied for the determination of MSG in food preparation (instant noodles). The results were compared to those obtained by a published HPLC method using t-test and F-test at 95% confidence interval; no statistically significant difference was found. Based on the analytical Eco-scale and the green analytical procedure index (GAPI), the developed method was assessed to be greener than the published HPLC method. The developed method offered advantages over other spectrophotometric reported methods and was convenient for routine determination of MSG in foodstuffs.

Background Ascorbic acid (ASC; vitamin C) is a weak chromophoric substance, so its presence cannot be determined directly by spectrophotometry. Objective This work aims to develop and validate a simple and ecofriendly analytical method for the determination of ASC concentration based on the reaction of ASC with the metal complex ferric salicylate. Method The visible absorbance of ferric salicylate was found to be inversely proportional to the concentration of ASC. The possible mechanism of the reaction between ASC and ferric salicylate was investigated: ferric salicylate was found to be reduced by ASC under the applied experimental conditions. Different parameters that may affect the reaction were also investigated: ferric salicylate concentration, pH, ionic strength, and the time of reaction. The optimum concentration of ferric salicylate was found to be 1000 µM and the optimum pH was 5.5. The developed method was validated according to ICH guidelines. Results The linearity range of the developed method was 5–70 µg/mL and the correlation coefficient was 0.9994. The limits of detection and quantitation were 0.38 µg/mL and 1.16 µg/mL, respectively. The method was successfully applied to the determination of ASC concentration in commercial Ruta-C60® tablets. The mean % recovery ± standard deviation was found to be 101.10 ± 0.70. The results were statistically compared to those obtained by a reported high performance liquid chromatographic method. Good agreement was observed. Conclusion The developed method is simple, fast, cost-effective, and suitable for routine pharmaceutical analysis of ASC. Highlights The developed method is more sensitive than the other spectrophotometric methods reported for determination of ASC.