ABSTRACT
The present study investigated the separation of bicyclic ß-amino acids with bicyclo[2.2.2]octane, bicyclo[3.1.1]heptane and cyclopenta[d][1,2]oxazole core structures by capillary electrophoresis using native cyclodextrins as well as neutral and charged derivatives as chiral selectors. The amino acids were derivatized with dansyl chloride to provide a UV chromophore. Separations were carried out at 20°C in a 48.5/40 cm, 50 µm fused-silica capillary at an applied voltage of 20 kV. Fifty millimolar sodium phosphate background electrolytes pH 2.5 and 7.2 containing either 5 or 30 mg/mL of the CDs were used. For the majority of the investigated CDs, enantioseparations could only be achieved at pH 2.5 when the analytes are positively charged. Successful enantioseparations as negatively charged analytes at pH 7.2 were only observed for few compounds. In the case of methyl-γ-cyclodextrin, opposite enantiomer migration order was observed in pH 2.5 or 7.2 background electrolytes. Dependence of the enantiomer migration order on the size of the cavity of the cyclodextrins was also found. Furthermore, the degree of methylation of ß-cyclodextrin derivatives affected the migration order of several analyte enantiomers.
Subject(s)
Amino Acids/isolation & purification , Bridged Bicyclo Compounds/chemistry , Cyclodextrins/chemistry , Electrophoresis, Capillary/methods , Octanes/chemistry , Oxazoles/chemistry , Amino Acids/analysis , Amino Acids/chemistry , Dansyl Compounds/chemistryABSTRACT
A capillary electrophoresis method was developed and validated for the determination of the purity of dapoxetine with regard to the related substances (3S)-3-amino-3-phenylpropan-1-ol, (3S)-3-(dimethylamino)-3-phenylpropan-1-ol, 1-naphthol and the enantiomer (R)-dapoxetine. The separation was based on a dual selector system, which was optimized by a fractional factorial resolution V + design followed by a central composite face centered design with star distance 1 and Monte Carlo simulations for defining the design space. The optimized background electrolyte consisted of a 50 mM sodium phosphate buffer, pH 6.3, containing 45 mg/mL sulfated γ-cyclodextrin and 40.2 mg/mL 2,6-dimethyl-ß-cyclodextrin. Separations were carried out in a 23.5/32 cm, 50 µm fused-silica capillary employing a separation voltage of 9 kV at 15 °C. Following robustness testing using a Plackett-Burman design the method was validated according to the International Council on Harmonization guideline Q2(R1) in the range of 0.05-1.0% relative to the dapoxetine concentration. The method was applied to the analysis of drug substance and a commercial tablet. Data regarding the enantiomeric purity of dapoxetine obtained by the capillary electrophoresis assay were comparable to the data obtained by an enantioselective HPLC method.
Subject(s)
Benzylamines/analysis , Drug Contamination , Electrophoresis, Capillary/methods , Naphthalenes/analysis , Naphthols/analysis , Selective Serotonin Reuptake Inhibitors/analysis , Benzylamines/standards , Computer Simulation , Monte Carlo Method , Naphthalenes/standards , Quality Control , Reproducibility of Results , Selective Serotonin Reuptake Inhibitors/standards , Stereoisomerism , TabletsABSTRACT
To characterize sulfoethyl cellulose el samples, a capillary electrophoresis method was developed and validated sulfoethyl cellulose el was hydrolyzed, and the resulting d-glucose derivatives were analyzed after reductive amination with 4-aminobenzoic acid using 150 mM boric acid, pH 9.5, as background electrolyte at 20°C and a voltage of 28 kV. Peak identification was derived from capillary electrophoresis with mass spectrometry using 25 mM ammonia adjusted to pH 6.2 by acetic acid as electrolyte. Besides mono-, di-, and trisulfoethyl d-glucose small amounts of disaccharides could be identified resulting from incomplete hydrolysis. The linearity of the borate buffer-based capillary electrophoresis method was evaluated using d-glucose in the concentration range of 3.9-97.5 µg/mL, while limits of detection and quantification derived from the signal-to-noise ratio of 3 and 10 were 0.4 ± 0.1 and 1.2 ± 0.3 µg/mL, respectively. Reproducibility and intermediate precision were determined using a hydrolyzed sulfoethyl cellulose el sample and ranged between 0.2 and 8.8% for migration times and between 0.3 and 10.4% for peak area. The method was applied to the analysis of the degree of substitution of synthetic sulfoethyl cellulose el samples obtained by variation of the synthetic process and compared to data obtained by elemental analysis.
ABSTRACT
Capillary electrophoresis (CE) is a versatile and flexible technique for analytical enantioseparations. This is due to the large variety of chiral selectors as well as the different operation modes including electrokinetic chromatography, micellar electrokinetic chromatography, and microemulsion electrokinetic chromatography. The chiral selector, which is added to the background electrolyte, represents a pseudostationary phase with its own electrophoretic mobility allowing a variety of different separation protocols. The present chapter briefly addresses the basic fundamentals of CE enantioseparations as well as the most frequently applied chiral selectors and separation modes. The practical example illustrates the separation of the enantiomers of a positively charged analyte using native and charged cyclodextrin derivatives as chiral selectors.
