title: Sensitivity improvement of circular dichroism detection in HPLC by using a low-pass electronic noise filter: Application to the enantiomeric determination purity of a basic drug.
abstract: The quality control of chiral drugs requires the determination of their enantiomeric purity. Nowadays, circular dichroism (CD) spectroscopy is gaining increasing importance in pharmaceutical analysis because of the commercially available CD detector in liquid chromatography. The separation of the two enantiomers of a basic drug (efaroxan) was achieved by high performance liquid chromatography using an amylose-derivated column with both UV and CD detections. A baseline-resolved separation (resolution: 5) was obtained after optimization of the mobile phase composition with hexane-ethanol-diethylamine (90:10:0.05; v/v/v). The use of a commercial low-pass electronic noise filter of the CD signal has improved the signal-to-noise ratio by a factor twelve and allowed the quantitation of each enantiomer in the 1.25-300 microg ml(-1) concentration range. The CD linear calibration curve, expressed in terms of stereoisomer height ratio versus concentration ratio, was plotted over the 0.4-6% range. A correlation coefficient greater than 0.999 was obtained by least-squares regression and the limit of detection for the distomer/eutomer ratio was estimated at 0.14%. Although the method validation showed good repeatability on the retention times (RSD < 0.9%), on the peak height ratios (RSD < 8.7%) of each enantiomer only up to 99.2% enantiomeric purity was achieved.
authors.affiliation: Institut de Chimie Organique et Analytique (ICOA), CNRS FR 2708, UMR 6005, Université d'Orléans, Orléans, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Lorin
authors.forename: Raphael
authors.initials: R
authors.lastname: Delepee
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Maurizot
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Ribet
authors.forename: Philippe
authors.initials: P
authors.lastname: Morin
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000032:analysis* / Q000737:chemistry; D001572:Benzofurans / Q000032:analysis* / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation; D002942:Circular Dichroism / Q000295:instrumentation*; D007093:Imidazoles / Q000032:analysis* / Q000737:chemistry; D012680:Sensitivity and Specificity; D013237:Stereoisomerism
chemical_list: D000317:Adrenergic alpha-Antagonists; D001572:Benzofurans; D007093:Imidazoles; C062597:efaroxan