Separation of Amino Acid 2,4-Dinitrophenyl-5-L-Valine Amide Diastereomeric Derivatives with High-Performance Planar Chromatography and Pressurized Planar Electrochromatography
Separation of 2,4-dinitrophenyl-5-L-valine amide derivatives of some amino acids (leucine, isoleucine, valine, asparagine, cysteine, tryptophane) L and D-enantiomers with high-performance thinlayer chromatography (HPTLC) and pressurized planar electrochromatography (PPEC) is presented. The separation mechanism in the PPEC technique involves two effects (partition and electrophoresis) whereas HPTLC system employs only one (partition). The separation process in both modes was carried out with the HPTLC RP-18 plates. Influence of the aqueous-organic mobile phase composition (acetonitrile concentration, buffer type, its pH) on migration distance of the solute zones is investigated and compared for both techniques. The PPEC system turns out to be more sensitive to buffer type and pH than HPTLC one. Additionally, the electrophoretic effect is responsible for different separation selectivity in PPEC system in comparison to that in HPTLC one. The retention of DL-diastereoisomer derivatives of amino acids is stronger in comparison with its LL-antipodes for both separation techniques. The statistic evaluation of the migration distance in PPEC and TLC systems shows similar RSD.