Separation of enantiomers of chiral basic drugs with amylose- and cellulose- phenylcarbamate-based chiral columns in acetonitrile and aqueous-acetonitrile in high-performance liquid chromatography with a focus on substituent electron-donor and electron-acceptor effects.

In this study, amylose- and cellulose-phenylcarbamate-based chiral columns with different chiral-selector (CS) chemistries were compared to each other for the separation of enantiomers of basic chiral analytes in acetonitrile and aqueous-acetonitrile mobile phases in HPLC. For two chemistries the amylose-based columns with coated and immobilized CSs were also compared. The comparison of CSs containing only electron-donating or electron-withdrawing substituents with those containing both electron-donating and electron-withdrawing substituents showed opposite results for the studied set of chiral analytes in the case of amylose and cellulose derivatives. Along with the chemistry of CS the focus was on the behavior of polysaccharide phenylcarbamates in acetonitrile versus aqueous acetonitrile as eluents. In agreement with earlier results, it was found that in contrast to the commonly accepted view, polysaccharide phenylcarbamates do not behave as typical reversed-phase materials for basic analytes either. In the range of water content in the mobile phase of up to 20-30% v/v the behavior of these CSs is similar to hydrophilic interaction liquid chromatography (HILIC)-type adsorbents. This means that with increasing water content in the mobile phase up to 20-30% v/v, the retention of analytes mostly decreases. The important finding of this study is that the separation efficiency improves for most analytes when switching from pure acetonitrile to aqueous acetonitrile. Therefore, in spite of reduced retention, the separation of enantiomers improves and thus, the HILIC-range of mobile phase composition, offering shorter analysis time and better peak resolution, is advantageous over pure polar-organic solvent mode. Interesting examples of enantiomer elution order (EEO) reversal were observed for some analytes based on the content of water in the mobile phase on Lux Cellulose-1 and Lux Amylose-2 columns.

Simultaneous determination of dextromepromazine and related substances 2-methoxyphenothiazine and levomepromazine sulfoxide in levomepromazine on a cellulose tris(4-methylbenzoate) chiral column.

A high-performance liquid chromatography method for the determination of dextromepromazine, levomepromazine sulfoxide and 2-methoxyphenothiazine in levomepromazine samples was developed. The separation of the analytes was achieved within 10 min on a stationary phase containing cellulose tris(4-methylbenzoate) as chiral selector. The mobile phase consisted of 0.1% diethylamine in methanol with a flow rate of 1.0 mL/min. The method was validated according to the International Council for Harmonization guideline Q2(R1). The detection limits based on a signal-to-noise ratio of 3 were in the range of 0.002 to 0.005 µg/mL. The method proved to be precise and accurate in the concentration range of 0.025-1.0 % for levomepromazine sulfoxide and 2-methoxyphenothiazine and 0.025% to 3.0% for dextromepromazine relative to a concentration of 0.1 mg/mL of levomepromazine, with the exception of levomepromazine sulfoxide at the 0.1% level. The method was subsequently applied to the analysis of finished pharmaceutical products as well as of reference substances of the European Pharmacopoeia.

Separation of enantiomers of selected chiral sulfoxides with cellulose tris(4-chloro-3-methylphenylcarbamate)-based chiral columns in high-performance liquid chromatography with very high separation factor.

The present study reports successful separations of enantiomers of selected chiral sulfoxides with very high separation factor in high-performance liquid chromatography by using chiral columns prepared with the chiral selector cellulose tris(4-chloro-3-methylphenylcarbamate). High separation factors were observed in polar organic, as well as in hydrocarbon-alcohol-type mobile phases. The key structural components of the solute for obtaining high chiral recognition are discussed as well as thermodynamic quantities of analyte adsorption on the chiral stationary phase were determined. Experiment aimed at the enantioselective extraction of racemates from solution are also described.