Quantitative gas chromatographic analysis of mandelic acid enantiomers

Abstract

A procedure was developed for the quantitative gas chromatographic (GC) analysis of mixtures of mandelic acid enantiomers. Past methods for the GC resolution of α-hydroxy acid enantiomers on optically active stationary phases are systematically reviewed, with special attention to mandelic acid, which is particularly prone to racemization during derivatization. Modification of an earlier procedure involving the conversions: mandelic acid → mandelyl chloride → N-propylmandelamide → O-trimethylsilyl-N-propylmandelamide finally permitted the preparation of O-trimethylsilyl-N-propylmandelamide on a macro scale with negligible racemization and allowed the precise GC analyses of mandelic acid enantiomers on a stainless-steel capillary column coated with N-docasanoyl-L-valine tert.-butylamide.