Quality by Design-Guided Development of a Capillary Electrophoresis Method for the Chiral Purity Determination of Ambrisentan

A quality by design approach utilizing experimental design methodologies was applied to develop a CE method to evaluate the enantiomeric purity of (S)-ambrisentan, a selective endothelin receptor antagonist used for the treatment of pulmonary arterial hypertension. Initial method scouting was performed by screening native cyclodextrins (CDs) as well as neutral CD derivatives and a positively charged derivative at pH 5 and pH 9, identifying γ-CD as suitable selector at pH 5. Upon defining the critical quality attributes and the critical process parameters, i.e., chiral resolution and run time, method development was performed by application of a screening design for the identification of the significant variables and, subsequently, by a response surface methodology for obtaining the design space. A Plackett–Burman design was employed for robustness testing. The final working point conditions used a background electrolyte composed of a 50-mM sodium acetate buffer, pH 4.0, containing 30 mM γ-CD in a 75-μm ID fused-silica capillary with an effective length of 40 cm at an applied voltage of 25 kV and a capillary temperature of 25 °C. The method was validated according to the ICH Q2(R1) guideline and allowed the determination of a relative concentration of the (R)-enantiomer of 0.1 %.

     

Advances of capillary electrophoresis enantioseparations in pharmaceutical analysis (2017–2020)

Capillary electrophoresis is a powerful technique for the analysis of polar chiral compounds and has been widely accepted for analytical enantioseparations of drug compounds in pharmaceuticals and biological media. In addition, many mechanistic studies have been conducted in an attempt to rationalize enantioseparations in combination with spectroscopic and computational techniques. The present review will focus on recent examples of mechanistic aspects and summarize recent applications of stereoselective pharmaceutical and biomedical analysis published between January 2017 and November 2020. Various separation modes including electrokinetic chromatography in combination with several detection modes including laser-induced fluorescence, mass spectrometry and contactless conductivity detection will be discussed. A general trend also observed in other analytical techniques is the application of quality by design principles in method development and optimization.     

Quality by design-guided development of a capillary electrophoresis method for the simultaneous chiral purity determination and impurity profiling of tamsulosin

Analytical Quality by Design principles using the design of experiments were applied for the development of a capillary electrophoresis method for the determination of enantiomeric purity and chemically related impurities of tamsulosin. From initial scouting experiments, a dual cyclodextrin (CD) system composed of sulfated β-CD and carboxymethyl-α-CD was selected as the chiral selector. A fractional factorial resolution V+ design was used for the identification of the critical process parameters, while a face-centered central composite design and Monte Carlo simulations were employed for final optimization and defining the design space of the method. The experimental conditions of the working point were: 30 mM sodium phosphate buffer, pH 3.0, containing 40 mg/mL sulfated β-CD and 7 mg/mL carboxymethyl-α-CD, capillary temperature 18°C, applied voltage -23 kV. Following the assessment of robustness by applying a Plackett-Burman design, the method was validated according to the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use guideline Q2(R1). The method allowed the quantification of the chiral impurity and three other related impurities at the 0.1 % level with acceptable accuracy and precision.     

Quality by design-assisted development of a capillary electrophoresis method for the enantiomeric purity determination of tenofovir

A CE method was developed and validated for the assessment of the chiral purity of the drug tenofovir applying a quality by design approach. Following selection of a quaternary ammonium β-CD as chiral selector, a fractional factorial resolution V+ design was employed for identification of the critical process parameters, while a central composite design served for method optimization. The final method used a 40/50.2 cm, 50 μm id fused-silica capillary, a BGE composed of a 100 mM sodium phosphate buffer, pH 6.4, containing 45 mg/mL quaternary ammonium β-CD, an applied voltage of 18 kV, and a capillary temperature of 22°C. Robustness was assessed by a Plackett–Burman design. The method was validated according to guideline Q2(R1) of the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use and enabled the determination of the (S)-enantiomer of tenofovir at the 0.1% level.