Enantiomeric separation of FMOC-amino acids by nano-LC and CEC using a new chiral stationary phase, cellulose tris(3-chloro-4-methylphenylcarbamate).

A novel polysaccharide-based chiral stationary phase (CSP), cellulose tris(3-chloro-4-methylphenylcarbamate), also known as Sepapak-2 or Lux Cellulose-2, has been evaluated for the enantiomeric separation of FMOC derivatives of amino acids. After mobile-phase optimization in nano liquid chromatography (nano-LC) the column enabled the enantiomeric separation of 19 out of 23 amino acids tested, indicating the high chiral recognition power of this new CSP. Subsequently, a comparison of the driving force employed (pressure or voltage) was carried out comparing nano-LC and CEC under the same conditions. Better peak efficiencies and resolution were observed by using CEC experiments, which enabled the chiral discrimination of 20 out of 23 amino acids tested. Finally, in order to show the potential of this new CSP, the determination of the content and the enantiomeric purity of the non-protein amino acid citrulline in food supplements was performed. For that purpose, the method was optimized, evaluated and applied to different commercial samples.

Enantioseparations with cellulose tris(3-chloro-4-methylphenylcarbamate) in nano-liquid chromatography and capillary electrochromatography.

Cellulose tris(3-chloro-4-methylphenylcarbamate) was coated onto native and aminopropylsilanized silica in order to prepare chiral stationary phases (CSPs) for enantioseparations using nano-liquid chromatography (nano-LC) and capillary electrochromatography (CEC). The effect of the chiral selector loading onto silica, mobile phase composition and pH, as well as separation variables on separation of enantiomers was studied. It was found that CSPs based on cellulose tris(3-chloro-4-methylphenylcarbamate) can be used for preparation of very stable capillary columns useful for enantioseparations in nano-LC and CEC in combination with polar organic mobile phases.

Comparative high-performance liquid chromatography enantioseparations on polysaccharide based chiral stationary phases prepared by coating totally porous and core-shell silica particles.

This article reports comparative high-performance liquid chromatographic separations of enantiomers with chiral stationary phases (CSPs) prepared by coating cellulose tris(4-chloro-3-methylphenylcarbamate) on totally porous and on core-shell type silica of comparable particle diameter. Several interesting observations were made: (1) the selectivity of separation was higher on core-shell type CSP compared to totally porous CSP at comparable content of chiral selector (polysaccharide derivative); (2) much flatter dependence of plate height on the mobile phase flow rate was observed for columns packet with CSP prepared with core-shell silica compared to the ones packed with CSPs prepared with totally porous particles; (3) at low mobile phase flow rates core-shell CSP provided lower resolving ability compared to a commercially available CSP having four times higher content of chiral selector along with higher retention of chiral analytes. However, at high flow rates core-shell type CSP performed similarly or better than the commercial column in regards of plate count (N) and peak resolution (R(s)) per column length and within a given total analysis time. The advantage of CSP prepared with core-shell silica is obvious from the viewpoint of plate numbers and resolution calculated per unit time (i.e. speed of analysis).