Kinetic study on reactive extraction of metoprolol enantiomers with cyclohexyl (D)-tartrate and boric acid as combined chiral selector

Abstract

Abstract This paper reports on the kinetic study on reactive extraction of metoprolol (MT) enantiomers using cyclohexyl (D)-tartrate (DT) and boric acid (BA) as combined chiral selector in a modified Lewis cell. An interfacial reaction model is applied to understanding the experimental data. The MT enantiomers are extracted enantioselectively from aqueous phase through the interfacial reaction among BA, DT and MT. Important factors that influence the kinetics of extraction are investigated. The optimal conditions for kinetic study were as follows: agitation speed of 75 rpm, interfacial area of 12.56 cm2, pH of 6, initial DT concentration of 0.075 mol/L, initial BA concentration of 0.1 mol/L, and initial MT concentration of 5 mmol/L at temperature of 5 °C. Important parameters concerning extraction kinetics are evaluated through multiple linear regression analysis of the experimental data. The interfacial reaction is 0.4, 0.6 and 1 order separately with respect to BA, MT and DT, and the total order of reaction is about 2. The forward rate constants have been found to be 5.24 × 10−4 L/(mol s) for (R)-MT and 2.73 × 10−4 L/(mol s) for (S)-MT.