Optimization of Reaction Parameters for the Synthesis of Chromium Methionine Complex Using Response Surface Methodology

Abstract

This study deals with a new and better protocol to prepare chromium methionine using aqueous ethanol solution as the reaction medium. Response surface methodology (RSM) coupled with Box-Behnken design was employed to model and optimize the operational parameters of this protocol. The ethanol content of aqueous ethanol, the molar ratio of methionine and Cr(III), reaction temperature, and reaction time were chosen as independent variables, and their combined effects on the conversion of Cr(III) (response 1) and the yield of chromium methionine (response 2) were investigated. The optimal values of the parameters were found to be the following: ethanol content of aqueous ethanol is 48.5%; n(Met)/n(NaOH)/n(CrCl3·6H2O) = 4.31:4.31:1; reaction time is 127 min; reaction temperature is 81.1 °C; initial Cr(III) concentration is 0.25 mol/L. The conversion of Cr(III) and the yield of chromium methionine are up to 99.79% and 99.23%, respectively, under the optimal conditions. The analysis of variance (ANOVA) and regression with R2 values of 0.9984 for the conversion of Cr(III) and 0.9974 for the yield of chromium methionine illustrate that the experimental results are in good agreement with the predicted values, and the models can be used to predict the synthesis of chromium methionine successfully.