Abstract
Separation of 5-(dimethylamino) naphthalene-1-sulphonyl (DNS-) derivatives of some amino acids (alanine, leucine, valine, phenylalanine) D- and L-enantiomers with high-performance thin layer chromatography (HPTLC) and pressurized planar electrochromatography (PPEC) both with β-cyclodextrin as the component of the mobile phase 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 W plates. Influence of variables such as: β-cyclodextrin concentration in the mobile phase and composition of the mobile phase on the migration distance of the solute zones is investigated.
Although HPTLC and PPEC systems enable to separate D- and L-DNS- amino acids the electrophoretic effect in PPECsystem is responsible for different separation selectivity in the latter one in comparison to that in first one. The retention of L-DNS- amino acids is stronger regarding their D-antipodes with both separation techniques. The repeatability of the results from separation of DNS-Ala enantiomers with PPEC and HPTLC technique is compared. Slightly worse standard deviation and RSD values for more retained enantiomer, researched with PPEC, are characteristics of this electromigrational technique.
In addition a new mode of β-cyclodextrin zone determination on the chromatographic plate is presented.
Keywords: β-cyclodextrin, chiral mobile phase, enantiomer separation, DNS-amino acids, HPTLC, PPEC.
Graphical Abstract
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