In the study of enzyme
catalyzed kinetic resolution of racemates, it is imperative to assay how the optical yield varies with chemical
conversion. In this paper, a method using one time injection to determine
enantiomeric excess and conversion of the stereoselective esterification of racemic
ibuprofen with n butanol catalyzed by lipase was developed with a commercially available HPLC CSP column Regis(S, S) Whelk 01. In the linear range of detector, all peak areas of products and substrates are proportional to their concentrations. Because the total mole concentration remains unchanged (equal to the initial value of ibuprofen) in the reaction process, the conversion could be calculated from the peak areas, provided the
ratio of
response factors was known. The calibration curves of two ibuprofen enantiomers with racemic ibuprofen as external standard were overlapped, indicating f i R =f i S . By investigating the variation of peak areas of products and substrates against conversion(determined by external standard), the ratio of peak area concentration response factor of ibuprofen butyl ester to that of unreacted ibuprofen was determined to be 1 through linear regressions, from which the conversion could be directly determined by the self normalization of the peak areas. With a mobile phase of IPA/hexane/HAc/triethylamine (15/85/0.2/0.05, V/V, flow rate 0.4mL/min), the resolution of ibuprofen enantiomers was sufficient for precise
Enantiomeric purity determination.
More abstracts about the Chiral HPLC Determination of Conversion and Enantiomeric Excess of Enzyme Catalyzed Stereoselective