Simultaneous separation of the enantiomers of cizolirtine and its degradation products by capillary electrophoresis

Enantioseparation and impurity determination of ambrisentan using cyclodextrin-modified micellar electrokinetic chromatography: Visualizing the design space within quality by design framework

A capillary electrophoresis method for the simultaneous determination of the enantiomeric purity and of impurities of the chiral drug ambrisentan has been developed following the Quality by Design principles. The selected separation system consisted of a micellar pseudostationary phase made by sodium dodecyl sulphate with the addition of γ-cyclodextrin. The effects of critical process parameters (capillary length, temperature, voltage, borate concentration, pH, sodium dodecyl sulphate concentration, γ-cyclodextrin concentration) on enantioresolution of ambrisentan and analysis time were extensively investigated by multivariate strategies involving a screening phase and Response Surface Methodology. The Design Space was defined with a desired probability level π≥90%, and the working conditions, with the limits of the Design Space, corresponded to the following: capillary length, 64.5cm; temperature, 22°C; voltage, 30kV (26-30kV); background electrolyte, 100mM borate buffer pH 9.20 (8.80-9.60), 100mM sodium dodecyl sulphate, 50mM (43-50mM) γ-cyclodextrin. A Plackett-Burman design was applied for robustness testing, and a method control strategy was established. The method was fully validated according to the International Conference on Harmonisation guidelines and was applied to ambrisentan coated tablets.

MEKC: An update focusing on practical aspects

This paper reviews recent methodological and instrumental advances in MEKC. Improvements in sensitivity arising from the use of on-line sample concentration (sweeping, stacking, and combination of both protocols) and derivatization (in-capillary reactions and coupling with flow-injection systems) and improvements in resolution obtained by changing the composition of the BGE (e.g., with organic modifiers, ionic liquids, nonionic and zwitterionic surfactants, mixed micelles, and vesicles) or using coated capillaries are discussed in detail. In addition, MS and LIF spectroscopy are examined in relation to their advantages and restrictions as applied to MEKC analysis. Some thoughts on potential future directions are also expressed.

Enantiomeric separation of cizolirtine and metabolites on amylose tris (3,5-dimethylphenyl carbamate) chiral stationary phase

The enantiomeric resolution of (+/-)-cizolirtine, (+/-)-cizolirtine-N-oxide, (+/-)-N-desmethylcizolirtine and (+/-)-5(alpha-hydroxybenzyl)-1-methylpyrazole was achieved on amylose tris (3,5-dimethylphenyl carbamate) chiral stationary phase known as Chiralpak AD using hexane/2-propanol/triethylamine (80:20:0.05, v/v/v) as the mobile phase. The flow rate of the mobile phase used was 1.0 ml/min with UV detection at 230 nm. The values of R(s) of the resolved enantiomers of (+/-)-cizolirtine, (+/-)-cizolirtine-N-oxide, (+/-)-N-desmethylcizolirtine and (+/-)-5(alpha-hydroxybenzyl)-1-methyl pyrazole were 1.20, 0.60, 1.16 and 1.15, respectively.