Influence of chromatographic descriptors on enantioresolution of a dihydropyridine and structurally related compounds

Abstract

The possibility to separate the enantiomers of a pharmacological active dihydropyridine and some of its possible by-products/metabolites was mapped using experimental design and multivariate analysis. All the tested racemates were enantioseparated using Chiral-AGP as the chiral stationary phase. All the investigated descriptor variables, mobile phase pH, organic modifier(s) and column temperature influenced the chiral recognition. The separation factor of the aprotic compound of pharmacological interest, H 324/38 (Solute No. 1), increased by increasing mobile phase pH, indicating changes in the conformation of the immobilized protein. The enantiomers of the major compound, a potential internal standard and the most important degradation product as well as the major metabolite, H 152/81 (Solute No. 5), could be separated simultaneously using a mix of two organic modifiers in the mobile phase. The presented work emphasises the use of experimental design and statistical multivariate evaluation. However, knowledge about the chromatographic system and the physical properties of the analytes, e.g., pK a values, are of highest importance in order to derive accurate conclusions.