Spectrophotometric determination of monosodium glutamate in instant noodles’ seasonings and Chinese salt by ligand exchange complexation

Abstract

A simple green spectrophotometric method was developed and validated for determination of non chromophoric substance; monosodium glutamate (MSG) by its reaction with a metal complexing agent; iron (III) salicylate. The color of the reagent measured at 525 nm fainted with increased absorbance at 299 nm upon addition of MSG, suggesting a ligand exchange reaction. Different parameters that may affect the reaction in the method were investigated such as: iron (III) salicylate concentration, pH, ionic strength and time of the reaction. The developed method was validated according to the guidelines of the International Conference on Harmonization (ICH). The linearity range was 250-2500 µM with correlation coefficient 0.9988. The limits of detection and quantitation were 71.5 µM and 216.76 µM. The developed method was successfully applied for determination of MSG in instant noodles’ seasoning and the Chinese salt and statistically compared to a reported HPLC method and good agreement was observed. The method shows advantages over other published spectrophotometric methods and was suitable for routine analysis of MSG in food preparations.