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CD System (cd + system)
Selected AbstractsCE assay for simultaneous determination of charged and neutral impurities in dexamphetamine sulfate using a dual CD systemELECTROPHORESIS, Issue 9 2010Sudaporn Wongwan Abstract A CE assay for the simultaneous determination of charged and uncharged potential impurities (1S,2S -(+)-norpseudoephedrine, 1R,2S -(,)-norephedrine, phenylacetone and phenylacetone oxime) of dexamphetamine sulfate including the stereoisomer levoamphetamine was developed and validated. The optimized background electrolyte consisted of a 50,mM sodium phosphate buffer, pH 3.0, containing 80,mg/mL sulfobutylether-,-CD and 25,mg/mL sulfated ,-CD. Separations were performed in 40.2/35,cm, 50 ,m id fused-silica capillaries at a temperature of 20°C and an applied voltage of ,10,kV. 1R,2S -(,)-ephedrine was used as internal standard. The assay was validated in the range of 0.05,1.0% for the related substances and in the range of 0.05,5.0% for levoamphetamine. The LOD was 0.01,0.02% depending on the analyte. The assay also allowed the separation of the E,Z-stereoisomers of phenylacetone oxime. The effect of the degree of substitution of sulfobutylether-,-CD was investigated. In commercial samples of dexamphetamine sulfate between 3.2 and 3.7% of levoamphetamine were found. Furthermore, phenylacetone and phenylacetone oxime could be observed at the LOD, indicating the synthetic origin of the investigated samples. [source] Determination of enantiomeric purity of a novel COX-2 anti-inflammatory drug by capillary electrophoresis using single and dual cyclodextrin systemsELECTROPHORESIS, Issue 9 2003Carlos Pérez-Maseda Abstract E-6087 is the most advanced compound among the cyclooxygenase-2 (COX-2) inhibitor drugs developed in our company. Its activity is mainly associated with the S(,)-enantiomer (E-6232), whereas the R(,)-enantiomer (E-6231) becomes an impurity whose content should be determined. Five main impurities and degradation products of E-6232 have been found (E-6144, E-6024, E-6072, E-6397 and E-6132), and some of them co-elute with the distomer when using a chiral high-performance liquid chromatography (HPLC) method. Consequently, we have optimized the separation of all the impurities from the two enantiomers of E-6087 by capillary electrophoresis (CE), in order to use the method for the enantiomeric purity determination of E-6232. The effect of the methanol (MeOH) content in the background electrolyte (BGE), the sulfobutyl ether-,-cyclodextrin (SBE-,-CD) and heptakis-(2,6-di- O -methyl)-,-cyclodextrin (DM-,-CD) concentration, and the capillary temperature have been studied. Separation of all compounds could be achieved in different systems, either in a single CD-system (with SBE-,-CD) or in a dual CD-system (with DM-,-CD as a neutral CD). By using the dual CD system a limit of detection (LOD) and a limit of quantitation (LOQ) of 0.03% and 0.1% of distomer, respectively, were achieved*. [source] First observation of natural circular dichroism spectra in the extreme ultraviolet region using a polarizing undulator-based optical system and its polarization characteristicsJOURNAL OF SYNCHROTRON RADIATION, Issue 4 2009Masahito Tanaka Natural circular dichroism (CD) spectra in the extreme ultraviolet (EUV) region down to a wavelength of 80,nm have been observed for the first time, using an alanine thin film deposited on sodium salicylate coated glass as a sample. Calibrated EUV-CD spectra of l -alanine exhibited a large negative peak at around 120,nm and a positive CD signal below 90,nm, which were roughly predicted by theoretical calculations. A CD measurement system with an Onuki-type polarizing undulator was used to obtain the EUV-CD spectra. This CD system, the development of which took five years, can be used to observe even weak natural CD spectra. The polarization characteristics of this system were also evaluated in order to calibrate the recorded CD spectra. [source] Enantiomeric separation of aminoglutethimide by capillary electrophoresis using native cyclodextrins in single and dual systemsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6-7 2003Adel M. Abushoffa Abstract Aminoglutethimide (AGT) is one of the few examples of chiral drugs that can be enantioseparated by capillary electrophoresis using any of the three native cyclodextrins: ,-, ,-, or ,-CD. A complete resolution of the enantiomers of this compound in cationic form could be achieved with each of the three CDs, using a pH 3 phosphoric acid-triethanolamine buffer. Affinity constants for AGT enantiomers with the three native CDs were determined, confirming that the highest selectivity was given by ,-CD while the strongest complexation was obtained with ,-CD. However, an opposite affinity pattern was observed with the latter. Selectivity was lower for AGT enantiomers in dual CD systems, compared to that obtained with a single selector at its optimal concentration, which confirms that dual systems are of more limited interest when the two selectors have a similar effect on the analyte mobility. These results are in good agreement with those predicted using recently developed mathematical models. [source] | ||||||||||