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Liquid Chromatographic Methods (liquid + chromatographic_methods)
Selected AbstractsHPLC enantioseparation of ,2 -homoamino acids using crown ether-based chiral stationary phaseJOURNAL OF SEPARATION SCIENCE, JSS, Issue 7 2009Róbert Berkecz Abstract RP high-performance liquid chromatographic methods were developed for the enantioseparation of eleven unusual ,2 -homoamino acids. The underivatized analytes were separated on a chiral stationary phase containing (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid as chiral selector. The effects of organic (alcoholic) and acidic modifiers, the mobile phase composition and temperature on the separation were investigated. The structures of the substituents in the ,-position of the analytes substantially influenced the retention and resolution. The elution sequence was determined in some cases: the S enantiomers eluted before the R enantiomers. [source] Investigation of lipophilicity of anticancer-active thioquinoline derivativesBIOMEDICAL CHROMATOGRAPHY, Issue 2 2007Marek Bajda Abstract The lipophilicity of a series of anticancer propargylthioquinoline derivatives has been investigated using chromatographic and computational methods. The parameters of relative lipophilicity (RMO and logk0) of the tested compounds were determined experimentally both by reversed-phase thin layer (RP-TLC), and high-performance liquid chromatographic methods (RP-HPLC, LiChrospher RP18 column), with mixtures of acetonitrile and water as mobile phases. Their phospholipophilicity (logk0IAM) was determined using immobilized artificial membrane HPLC (IAM. PC DD2 Regis column). Mobile phase acetonitrile concentrations were in the ranges 50,90% (RP-TLC), 55,90% (RP-HPLC) and 35,60% (IAM-HPLC). The RM, logk and logkIAM values of the compounds investigated were linearly dependent on acetonitrile concentration. The analysis led to the calculation of RMO, logk0 and logk0IAM parameter values for each of the tested compounds. Their partition coefficients (logP) were also calculated with the Pallas and CAChe programs. The obtained results indicated that, among experimental methods, both RP-TLC and RP-HPLC gave similar results, and these methods enable the determination of lipophilicity of derivatives of thioquinolines. Using the IAM-HPLC technique a simple method of estimation of phospholipoplilicity was described. The CAChe program might better predict calculated lipophilicity logP values, and therefore is a useful tool for the early stage of design of new propargyl thioquinolines. Copyright © 2006 John Wiley & Sons, Ltd. [source] Comparison between micellar liquid chromatography and capillary zone electrophoresis for the determination of hydrophobic basic drugs in pharmaceutical preparationsBIOMEDICAL CHROMATOGRAPHY, Issue 1 2007S. Torres-Cartas Abstract The determination of highly hydrophobic basic compounds by means of conventional reversed-phase liquid chromatographic methods has several drawbacks. Owing to the characteristics of micellar liquid chromatography (MLC) and capillary electrophoresis (CE), these techniques could be advantageous alternatives to reversed-phase chromatographic methods for the determination of these kinds of compounds. The objective of this study was to develop and compare MLC and CE methods for the determination of antipsychotic basic drugs (amitryptiline, haloperidol, perphenazine and thioridazine) in pharmaceutical preparations. The chromatographic determination of the analytes was performed on a Kromasil C18 analytical column; the mobile phase was 0.04 m cetyltrimethylammonium bromide (CTAB), at pH 3, containing 5% 1-butanol, at a flow rate of 1 mL/min. The CE separation was performed in a fused-silica capillary with a 50 mm tris-(hydroxymethyl)-aminomethane buffer, pH 7, at an applied voltage of 20 kV, using barbital as internal stardard. The proposed methods are suitable for a reliable quantitation of these compounds in the commercial tablets and drops in terms of accuracy and precision and require a very simple pre-treatment of the samples. By comparing the performance characteristics and experimental details of the MLC and CE methods we conclude that CE seems to be slightly better than MLC in the determination of highly hydrophobic compounds in pharmaceuticals in terms of resolution and economy, taking into account that the limits of detection are not a handicap in pharmaceutical samples. Copyright © 2006 John Wiley & Sons, Ltd. [source] High-performance liquid chromatographic chiral separation of ,2 -homoamino acidsCHIRALITY, Issue 9 2009Zoltán Pataj Abstract Reversed-phase high-performance liquid chromatographic methods were developed for the separation of enantiomers of eleven unnatural ,2 -homoamino acids on chiral stationary phases containing macrocyclic glycopeptides (teicoplanin-containing Chirobiotic T and T2) or the macrocyclic peptide teicoplanin aglycone (Chirobiotic TAG) as chiral selectors. The effects of the organic modifier, the mobile phase composition, temperature, and the structures of the analytes on the separations were investigated. Separations were carried out at constant mobile phase compositions in temperature range 7,45°C and the changes in enthalpy, ,(,H°), entropy, ,(,S°), and free energy, ,(,G°), were calculated. The ,,(,G°) values obtained on the three columns indicated that Chirobiotic TAG, without sugar units, may promote the interactions of the enantiomers of ,2 -homoamino acids with branched alkyl or aryl side-chains, whereas for ,2 -homoamino acids with alkyl side-chains Chirobiotic T and T2 seem to be more favorable. The elution sequence was determined in some cases and was observed to be R < S. Chirality, 2009. © 2008 Wiley-Liss, Inc. [source] | ||||||||||