Molecular imprinting science and technology: a survey of the literature for the years up to and including 2003

Molecularly imprinted polymers for the enantioseparation of chiral drugs.

The current state of chiral separations by thin-layer chromatography using chiral stationary phases is reviewed. Both stationary phases essentially constituted by the chiral selector and those obtained by the impregnation of achiral plates with appropriate chiral selectors are described. Particular attention is paid to commercial and non-commercial cellulose and cellulose-derivative plates, as well as commercially available Chiralplate™, which are currently the most widely used. Some of the most important results obtained to date are reported and discussed; the examples provided illustrate the very wide range of structurally different solutes that can be readily resolved into their enantiomers by planar chromatographic methods. Special attention is paid to the discussion of the retention and resolution factors that influence chiral discrimination. The quantitative analysis of enantiomers is also discussed, especially from the point of view of determination of enantiomeric purity.

Thin-layer chromatography enantioseparations on chiral stationary phases: a review.

Direct enantiomeric resolution of commonly used five racemic β-adrenolytics, namely, bisoprolol, atenolol, propranolol, salbutamol and carvedilol has been achieved by thin layer chromatography using bovine serum albumin (BSA) as chiral additive in stationary phase. Successful resolution of the enantiomers of all racemic β-adrenolytics was achieved by use of different composition of simple organic solvents having no buffer or inorganic ions. The effect of variation in pH, temperature, amount of BSA as the additive, and composition of mobile phase on resolution was systematically studied. Spots were visualized in iodine vapors. Native enantiomers for each of the five analytes were isolated and identified and their elution order was determined. The limit of detection was found to be 0.7, 1.2, 0.84, 1.6 and 0.9 μg (per spot) for each enantiomer of bisoprolol, atenolol, propranolol, salbutamol and carvedilol, respectively.

/pdf/thin-layer-chromatographic-resolution-of-some-b-adrenolytics-1uo4q5odqc.pdf

Thin Layer Chromatographic Resolution of Some β-adrenolytics and a β2-Agonist Using Bovine Serum Albumin as Chiral Additive in Stationary Phase

The high performance liquid chromatography (HPLC) enantioseparation of four β-blocking agents metoprolol, bisoprolol, propranolol and atenolol was performed on amylose tris-(3,5dimethylphenylcarbamate) chiral stationary phase using n-hexane-ethanol-diethylamine (DEA) as the mobile phase and related chiral recognition mechanisms were discussed. Enantiomeric separation of the four β-blockers was a result of more than one type of interaction between solutes and CSP. Besides hydrogen bonding, there was another type interaction that was independent of solvent polarity and responsible for enantiomeric selectivity, such as π-π interactions. Both the groups close to the chiral centers and the substituent groups on the phenyl rings, which were far away from the chiral centers, could contribute to the good separation. The separations of the four β-blocker enantiomers were all enthalpy driven process. In the range of 293–308K (20–35 °C), as the temperature increased, the retention as well as the resolution decreased. The molecular size rather than concentration of the alcohol modifiers affected the resolution and retention.

http://ijpr.sbmu.ac.ir/pdf_1491_cf16c16883ef8800f00283686fb9e8f6.html

Chiral Recognition Mechanisms of four β-Blockers by HPLC with Amylose Chiral Stationary Phase.

Molecular imprinted polymers (MIPs) of S-timolol were prepared as chiral stationary phases (CSPs) in thin layer chromatography (TLC). The resolution of the enantiomers of some cardiovascular drugs, including propranolol, atenolol, timolol, nadolol, nifedipine and verapamil were investigated on these CSPs. A mobile phase system of either methanol or acetonitrile was used and the effects of acetic acid content of the mobile phases were also investigated. The best resolution was achieved for enantioseparation of propranolol, timolol and atenolol on plates based on MIP of (-)-S-timolol using methacrylic acid as functional monomer (alpha = 1.52, 1.6, 1.59) respectively, using acetonitrile containing 5% acetic acid and (alpha = 1.47, 1.52, 1.5) in methanol containing 1% acetic acid as mobile phases. The results obtained show that TLC based on MIPs could be applied in the direct separation of several beta-adrenergic drugs. As the side chains on beta-blockers are similar, it is possible that this method could also be used for the resolution of other racemates in this family of drugs. Racemic drugs structurally related to print molecule, were completely resolved into two spots with the MIP plates. In general the retention of (+)-R-isomers was greater than that of (-)-S-isomers, indicating lower stereoselectivity of the MIPs to the dextrorotatory isomers. The method offers a rapid, sensitive and reliable method for quality control for these drugs.

Direct enantiomeric resolution of some cardiovascular agents using synthetic polymers imprinted with (-)-S-timolol as chiral stationary phase by thin layer chromatography.

H. Y. Aboul-Enein

Papers

Direct enantiomeric resolution of some cardiovascular agents using synthetic polymers imprinted with (-)-S-timolol as chiral stationary phase by thin layer chromatography.