Rekha Shah | PubMed Health

PubMed2004

Enantioseparation of hydrochloride salts using carbon dioxide-based mobile phases with on-line polarimetric detection.

Most HPLC enantioseparations of amine analytes are performed using normal-phase systems containing mobile phases of heptane with ethanol (or 2-propanol) and an amine additive. Since salt-forms of amine analytes are usually insoluble in normal-phase eluents, free-base forms are synthesized for preparative chromatography. It would be highly desirable to directly chromatograph salt forms of amine analytes using mobile phases of carbon dioxide (CO(2)) and methanol (MeOH). Such separations would be readily suitable for preparative chromatography, since most amine salts are highly soluble in MeOH. In this article, advantages are shown for the use of supercritical fluid chromatography (SFC) instrumentation with tandem UV and polarimetric detection for confirming enantioseparation as well as for determining optimum preparative column injections. Examples are shown for racemic mixtures of propranolol HCl (I), thioridazine HCl (II), tramadol HCl (III), and flurbiprofen (IV), all of which resolved on Chiralpak AD-H chiral stationary phase using mobile-phase systems of CO(2) and MeOH without the use of basic or acidic additives.

Journal Article↗

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Fast method development and rapid analysis using a screening approach for enantiomeric separations in capillary electrophoresis.

In order to speed up the trial-and-error process during enantioselective capillary electrophoresis methods development, a systemized approach is proposed to develop methods by applying several screening methods in the search for an initial separation. Screening methods combine high selectivity with broad applicability and are applied to find an initial enantiomeric separation during early pharmaceutical development (pre-Phase 1 to Phase 1). The goal is to achieve enantiomeric separation rapidly in order to characterize the chiral purity of pharmaceutical products. Dedicated, highly efficient screening methods are suggested for basic, neutral, and acidic compounds. In these screening methods, multiple chiral selectors are applied in mixtures at different buffer pH values. For the compounds studied, the technique allows fast method development. Furthermore, it is potentially applicable to a wide range of low-molecular-weight compounds and permits rapid analysis at low cost, since runs are performed in inexpensive, bare silica capillaries using ordinary buffer systems with only typical cyclodextrins as the selector. Along with simplicity and robustness, the approach results in sufficient efficacy (i.e., it is easy, straightforward, and reproducible, with a high success rate). Typical pharmaceutical applications are described. The major advantage of the screening approach to methods development is the decrease in development cycle time. The total screening time for one compound was about 5.3 hr on one CE instrument.

Complex Mixtures↗