Separation of enantiomers by high performance liquid chromatography using chiral eluents

Abstract

Abstract Simple procedures are presented for separating the enantiomers of α‐methyldopa, 5‐hydroxytryptophan, tryptophan, triiodothyronine and thyroxine, which require neither special sorbents nor difficult‐to‐obtain or unstable reagents. The method for α‐methyldopa, 5‐hydroxytryptophan and tryptophan is based on the use of L‐phenylalanine copper complex as the chiral constituent of the mobile phase; LiChrosorb® RP‐18 serves as the stationary phase. The procedure for triiodothyronine and thyroxine is grounded on the L‐proline copper complex as the chiral reagent and LiChrosorb® Si 60 as the stationary phase. In all observed cases, the D‐enantiomer is eluted prior to the respective L‐enantiomer. Chirality inversion of the mobile phase (application of the D‐phenylalanine copper complex) reverses the order of elution; a racemic eluent (DL‐phenylalanine copper complex) leads to no separation. In addition to the enantiomers of α‐amino acids, the enantiomers of α‐hydroxy acids (mandelic acid) can be separated.