Resolution Factor (resolution + factor)

Distribution by Scientific Domains


Selected Abstracts


Extended application of a chiral stationary phase based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid to the resolution of N -(substituted benzoyl)-,-amino acid amides

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 10 2006
Guanghui Tan
Abstract A chiral stationary phase (CSP 1) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid was applied to the resolution of N -(substituted benzoyl)-,-amino acid amides and esters. N -(Substituted benzoyl)-,-amino acid amides were well resolved using a mixture of acetic acid-triethylamine-acetonitrile (0.01 : 0.05 : 100, v/v/v) as an optimum mobile phase while N -(substituted benzoyl)-,-amino acid esters were not resolved at all. In contrast, both N -(substituted benzoyl)-,-amino acid amides and esters were not resolved at all or resolved very poorly on another CSP (CSP 2), which lacks the two N,H hydrogens of the amide tethers of CSP 1. Among the substituents on the benzoyl group of analytes, the nitro group was the best for good resolution of analytes on CSP 1. From these results, the two N,H hydrogens of the amide tethers of CSP 1, the carbonyl oxygen of the amide group of analytes, and the nitro group on the benzoyl group of analytes were concluded to play significant roles in chiral recognition. In addition, various N -(3,5-dinitrobenzoyl)leucine amides with different lengths of N -alkylamide chains were resolved on CSP 1 and N -(3,5-dinitrobenzoyl)leucine N -propylamide was found to show the best chiral recognition in terms of the separation (, = 1.30) and the resolution factor (RS = 3.17). [source]


Direct high-performance liquid chromatographic separation of the enantiomers of venlafaxine and 11 analogs using amylose-derived chiral stationary phases

CHIRALITY, Issue 6 2009
Salvatore Caccamese
Abstract A direct liquid chromatographic enantioselective separation of venlafaxine and 11 analogs was obtained in the normal phase mode using Chiralpak AD. For some compounds, a comparison between the enantioseparation using coated and immobilized amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phases (Chiralpak AD and Chiralpak IA, respectively) was made. The best separations were achieved on Chiralpak AD with ethanol as alcoholic modifier in a mobile phase made basic by DEA addition: separation factor ranges between 2.08 and 1.15 and resolution factor between 7.0 and 1.0. Using the same CSP and 2-propanol doped with TFA as acidic modifier, 10 compounds were enantioseparated with separation factor ranging between 1.40 and 1.04 and resolution factor between 3.1 and 0.3. The use of ethanol as alcoholic modifier also has the advantage of better solubility of the compounds in the mobile phase. The nature of the substituent (electron donating or withdrawing) affects in general the separation factor. A memory effect that involves a long equilibration time of the CSP is present when switching from an acidic mobile phase to a basic one. Chirality, 2008. © 2009 Wiley-Liss, Inc. [source]


Chiral separation of rac -Ornidazole and detection of the impurity of (R)-Ornidazole in (S)-Ornidazole injection and raw material

CHIRALITY, Issue 8 2006
Jianquan Huang
Abstract (S)-Ornidazole is a subject of research as an antifertility agent in male animals at present. However, there seems to be no relative report on chiral separation for rac -Ornidazole, which has been used as an effective medicine for more than 30 years. In this article, the chiral separation of rac -Ornidazole on a Chiralcel OB-H column based on normal-phase high-performance liquid chromatography (NP-HPLC) is investigated and the methodology for detection of impurity of (R)-Ornidazole in (S)-Ornidazole injection and raw material is established. The novel mobile phase is utilized by mixing n -hexane, methanol and isopropyl alcohol (95:4:1, v/v/v) instead of the typical mobile phase of n -hexane and isopropyl alcohol, although the methanol, which offers a good resolution factor for the enantiomeric separation in this system, is not recommended on the Chiralcel OB-H column according to the instruction supplied by Daicel Chemical Ind., LTD (Japan). Chirality, 2006. © 2006 Wiley-Liss, Inc. [source]


Determination of quinocide as impurity in primaquine tablets by capillary zone electrophoresis

BIOMEDICAL CHROMATOGRAPHY, Issue 5 2009
Abdalla A. Elbashir
Abstract A capillary zone electrophoretic method has been developed and validated for the determination of the impurity quinocide (QC) in the antimalarial drug primaquine (PQ). Different buffer additives such as native cyclodextrins and crown ethers were evaluated. Promising results were obtained when either , -cyclodextrin (, -CD) or 18-crown-6 ether (18C6) were used. Their separation conditions such as type of buffer and its pH, buffer additive concentration, applied voltage capillary temperature and injection time were optimized. The use of 18C6 offers slight advantages over , -CD such as faster elution times and improved resolution. Nevertheless, migration times of less than 5 min and resolution factors (Rs) in the range of 2,4 were obtained when both additives were used. The method was validated with respect to selectivity, linearity, limits of detection and quantitation, analytical precision (intra- and inter-day variability) and repeatability. Concentrations of 2.12 and 2.71% (w/w) of QC were found in pharmaceutical preparations of PQ from two different manufacturers. A possible mechanism for the successful separation of the isomers is also discussed. Copyright © 2008 John Wiley & Sons, Ltd. [source]


The role of ,-acidic and ,-basic chiral stationary phases in the high-performance liquid chromatographic enantioseparation of unusual ,-amino acids

CHIRALITY, Issue 3 2009
István Ilisz
Abstract The application of 3,5-dimethylphenyl-carbamoylated-,-cyclodextrin (Cyclobond I 2000 DMP) and 2,6-dinitro-4-trifluoromethylphenyl-ether-,-cyclodextrin-based (Cyclobond DNP) chiral stationary phases for the high-performance liquid chromatographic enantioseparation of unusual ,-amino acids is reported. The investigated amino acids were saturated or unsaturated alicyclic ,-3-homo-amino acids and bicyclic ,-amino acids. Prior to chromatographic analyses, all amino acids were transformed to N- 3,5-dinitrobenzoyl- or N -3,5-dimethylbenzoyl form to ensure a ,-acidic or ,-basic function and to enhance the ,-acidic-,-basic interactions between analytes and chiral selectors. Chromatographic results are given as retention, separation and resolution factors. The chromatographic conditions were varied to achieve optimal separation. The sequence of elution of the enantiomers was determined in some cases. Chirality, 2009. © 2008 Wiley-Liss, Inc. [source]