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Analytical Separation (analytical + separation)
Selected AbstractsOn-line desalting and determination of morphine, morphine-3-glucuronide and morphine-6-glucuronide in microdialysis and plasma samples using column switching and liquid chromatography/tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2005Jörgen Bengtsson A sensitive and reproducible method for the determination of morphine and the metabolites morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) was developed. The method was validated for perfusion fluid used in microdialysis as well as for sheep and human plasma. A C18 guard column was used to desalt the samples before analytical separation on a ZIC HILIC (hydrophilic interaction chromatography) column and detection with tandem mass spectrometry (MS/MS). The mobile phases were 0.05% trifluoroacetic acid (TFA) for desalting and acetonitrile/5,mM ammonium acetate (70:30) for separation. Microdialysis samples (5,µL) were directly injected onto the system. The lower limits of quantification (LLOQ) for morphine, M3G and M6G were 0.50, 0.22 and 0.55,ng/mL, respectively, and the method was linear from LLOQ to 200,ng/mL. For plasma, a volume of 100,µL was precipitated with acetonitrile containing internal standards (deuterated morphine and metabolites). The supernatant was evaporated and reconstituted in 0.05% TFA before the desalting process. The LLOQs for sheep plasma were 2.0 and 3.1,ng/mL and the ranges were 2.0,2000 and 3.1,3100,ng/mL for morphine and M3G, respectively. For human plasma, the LLOQs were 0.78, 1.49 and 0.53,ng/mL and the ranges were 0.78,500, 1.49,1000 and 0.53,500,ng/mL for morphine, M3G and M6G, respectively. Copyright © 2005 John Wiley & Sons, Ltd. [source] Oriented Ensembles in Ultrafast Electron DiffractionCHEMPHYSCHEM, Issue 7 2006J. Spencer Baskin Abstract Electron scattering expressions are presented which are applicable to very general conditions of implementation of anisotropic ultrafast electron diffraction (UED) experiments on the femto- and picosecond time scale. "Magic angle" methods for extracting from the experimental diffraction patterns both the isotropic scalar contribution (population dynamics) and the angular (orientation-dependent) contribution are described. To achieve this result, the molecular scattering intensity is given as an expansion in terms of the moments of the transition-dipole distribution created by the linearly polarized excitation laser pulse. The isotropic component (n=0 moment) depends only on population and scalar internuclear separations, and the higher moments reflect bond angles and evolve in time due to rotational motion of the molecules. This clear analytical separation facilitates assessment of the role of experimental variables in determining the influence of anisotropic orientational distributions of the molecular ensembles on the measured diffraction patterns. Practical procedures to separate the isotropic and anisotropic components of experimental data are evaluated and demonstrated with application to reactions. The influence of vectorial properties (bond angles and rotational dynamics) on the anisotropic component adds a new dimension to UED, arising through the imposition of spatial order on otherwise randomly oriented ensembles. [source] Utility of ionic liquids in analytical separationsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 11 2007Shahab A. Shamsi Abstract Ionic liquids (ILs), as separation media, have made significant contributions in the past decades in advancing research in gas chromatography (GC), liquid chromatography (LC), and capillary electrophoresis (CE). This review, covering reports published from the mid 1980s to early 2007, shows how ILs have been used so far in separation science, originally primarily as GC stationary phases and later as mobile phase additives (both millimolar and major percent levels) for LC and CE. Representative GC and LC chromatograms as well as CE electropherograms are shown. In addition, the very recent findings on the development of ionic liquids with surfactant properties and its applications for chiral and achiral analysis are discussed. [source] Comprehensive two-dimensional gas chromatography-mass spectrometry: A reviewMASS SPECTROMETRY REVIEWS, Issue 2 2008Luigi Mondello Abstract Although comprehensive two-dimensional gas chromatography (GC,×,GC) has been on the scene for more than 15 years, it is still generally considered a relatively novel technique and is yet far from being fully established. The revolutionary aspect of GC,×,GC, with respect to classical multidimensional chromatography, is that the entire sample is subjected to two distinct analytical separations. The resulting enhanced separating capacity makes this approach a prime choice when GC analysts are challenged with highly complex mixtures. The combination of a third mass spectrometric dimension to a GC,×,GC system generates the most powerful analytical tool today for volatile and semi-volatile analytes. The present review is focused on the rather brief, but not scant, history of comprehensive two-dimensional GC-MS: the first experiments were carried out at the end of the 1990s and, since then, the methodology has been increasingly studied and applied. Almost all GC,×,GC-MS applications have been carried out by using either a time-of-flight or quadrupole mass analyzer; significant experiments relative to a variety of research fields, as well as advantages and disadvantages of the MS systems employed, are discussed. The principles, practical and theoretical aspects, and the most significant developments of GC,×,GC are also described. © 2008 Wiley Periodicals, Inc., Mass Spec Rev 27:101,124, 2008 [source] | ||||||||||