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M ID (m + id)
Terms modified by M ID Selected AbstractsCapillary electrophoretic chiral separation of hydroxychloroquine and its metabolites in the microsomal fraction of liver homogenatesELECTROPHORESIS, Issue 5-6 2006Carmem Dickow Cardoso Abstract A rapid, selective, and low-cost chiral capillary electrophoretic method was developed for the simultaneous analysis of hydroxychloroquine (HCQ) and its three chiral metabolites: desethylchloroquine (DCQ), desethylhydroxychloroquine (DHCQ), and bisdesethylchloroquine (BDCQ) in the microsomal fraction of liver homogenates. After liquid,liquid extraction using toluene as extracting solvent, the drug and metabolites were resolved on a fused-silica capillary (50,,m ID, 50,cm total length, and 42,cm effective length), using 100,mmol/L of Tris/phosphate buffer, pH,9.0 containing 1% w/v sulfated-,-CD and 30,mg/mL hydroxypropyl-,-CD. Detection was carried out at 220,nm. The extraction procedure was efficient in removing endogenous interferents, and low values (,15%) for CVs and deviation from theoretical values were demonstrated for both within-day and between-day assays. The quantitation limit was 125,ng/mL with linear response over the 125,2000,ng/mL of concentration range for all metabolites. After validation, the method was used for an in vitro metabolism study of HCQ. The major HCQ metabolite formed by microsomal enzymes was (,)-(R)-DHCQ. [source] Optimization of the chiral resolution of baclofen by capillary electrophoresis using ,-cyclodextrin as the chiral selectorELECTROPHORESIS, Issue 12-13 2003Imran Ali Abstract The chiral resolution of baclofen was achieved by capillary electrophoresis using a fused-silica capillary (60 cm×75 ,m ID). The background electrolyte (BGE) was phosphate buffer (pH 7.0, 50 mM)-acetonitrile (95:5 v/v) containing 10 mM ,-cyclodextrin. The applied voltage was 15 kV. The values of , and Rs were 1.06 and 1.00, respectively. The electrophoretic conditions were optimized varying the pH and the ionic strength of the BGE, concentrations of ,-cyclodextrin and acetonitrile and the applied voltage. [source] Fluid dynamics in coal liquefaction reactors using neutron absorption tracer techniqueAICHE JOURNAL, Issue 8 2000Naohide Sakai Hydrodynamic properties in the coal liquefaction reactors at the Kashima pilot plant, which was constructed based on the NEDOL process, were investigated using the neutron absorption tracer technique. The reactor system is composed of three vessels, each with 1.0 m ID and 11.8 m in height. The gas velocity in the reactors under coal liquefaction conditions was estimated using a reaction simulator that contained reaction rates and vapor,liquid equilibrium. The axial dispersion coefficients in the first and third reactors at superficial gas velocities of 0.06,0.07 m/s were much smaller than those reported for air,water systems under ambient conditions. This suggests that the pilot-plant reactors operated fundamentally in the homogeneous bubble flow regime. [source] Analysis of isomeric tropane alkaloids from Schizanthus grahamii by very fast gas chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2006Stefan Bieri Abstract This study presents a very fast GC analysis applied for the baseline separation of isomeric tropane alkaloids extracted from the stem-bark of Schizanthus grahamii (Solanaceae). The work provided a challenging application where isothermal analysis in conjunction with very short narrow bore columns (3 m×100 ,m ID and 1.5 m×50 ,m ID) was particularly suited for the speeding up. Experimental parameters were used in the optimisation steps, including selection of stationary phase, temperature, internal column diameter and optimal practicable gas velocity. Some considerations about sample injection in fast isothermal analysis are also briefly presented. Finally, the investigated approach allowed a very fast baseline separation of four positional and configurational isomers in less than 9 s. [source] Enantiomeric separation of mirtazapine and its metabolites by nano-liquid chromatography with UV-absorption and mass spectrometric detectionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2005Salvatore Fanali Abstract Mirtazapine (MIR) and two of its main metabolites, namely, 8-hydroxymirtazapine and N -desmethylmirtazapine, were separated in totheir enantiomers by nanoLC in a laboratory-made fused-silica capillary column (75 ,m ID) packed with a vancomycin-modified silica stationary phase. The simultaneous separation of the three couples of the studied enantiomers was achieved in less than 33 min, using an experimentally optimized mobile phase delivered in the isocratic mode. Optimization of the mobile-phase composition was achieved by testing the influence of the buffer pH and concentration, the water concentration, the organic modifier type and concentration, and on the retention and resolution of the analytes. The optimum mobile-phase composition contained 500 mM ammonium acetate pH 4.5/water/MeOH/MeCN, 1 : 14 : 40 : 45 v/v/v/v. Using a UV detector at 205 nm, the method was validated studying several experimental parameters such as LOD and LOQ, intraday and interday repeatability, and linearity. Good results were achieved: LOD and LOQ were in the range 5,15 and 10,40 ,g/mL, respectively (the highest value was obtained for the DEMIR enantiomers); correlation coefficients, 0.9993,0.9999; the intraday and interday precision was acceptable (RSD < 2%) using an internal standard. The method was tested for the separation of the studied enantiomers in an extracted (solid-phase) serum sample spiked with standard racemic mixture of MIR and its two metabolites. Finally, the nanoLC system was connected to a mass spectrometer through a nanoelectrospray interface and the MS, MS2, and MS3 spectra were acquired showing the potential of the system used for characterization and identification of the separated analytes. [source] Detectability enhancement of spectrophotometric detectors by the use of multidimensional gas chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 18 2002Juan Carlos Medina Abstract Multidimensional gas chromatography (2D GC) is demonstrated as a way to improve limits of detectability of spectrophotometric detectors. UV and IR detectors are generally less sensitive than mass spectrometers or other GC detectors. This has placed some limitations on the useful capabilities provided by spectrophotometric detectors, such as the ability to provide structure-related information for a particular analyte. In this paper, we report results from interfacing a 2D GC instrument to a UV detector. Symmetry factor and the ratio of retention time divided by peak width did not show deterioration of the quality of chromatography when a megabore column was used with this detector. Furthermore, an increase in the limits of detectability over that attainable in a single-column system was realized by using the 2D GC system. However, the low flow (1 mL/min) imposed by the use of a microbore column (250 ,m ID) caused significant tailing when the UV detector was used. [source] Determination of uranium, iron, copper, and nickel from ore samples by MEKC using N,N,-ethylene bis(salicylaldimine) as complexing reagentELECTROPHORESIS, Issue 3 2008Muhammed Aslam Mirza Abstract An analytical procedure has been developed for the separation of dioxouranium(VI), iron(III), copper(II), nickel(II), cobalt(II), cobalt(III), palladium(II), and thorium(IV) by MEKC using N,N,-ethylene bis(salicylaldimine) (H2SA2en) as a complexing reagent with total runtime <4.5,min. SDS was used as micellar medium at pH,8 with sodium tetraborate buffer (0.1,M). An uncoated fused-silica capillary with an effective length of 50,cm×75,,m id was used with an applied voltage of 30,kV with photodiode array detection at 231,nm. Linear calibrations were obtained within 0.111,1000,,g/mL of each element with LODs within 37,325,ng/mL. The developed method was tested for analysis of uranium ore samples indicating its presence within 103,1789,,g/g with RSD within 0.79,1.87%. Likewise copper, nickel, and iron in their combined matrix were also simultaneously determined with RSD 0.4,1.6% (n,=,6). [source] Determination of glyoxal and methylglyoxal in the serum of diabetic patients by MEKC using stilbenediamine as derivatizing reagentELECTROPHORESIS, Issue 21 2007Muhammad A. Mirza Abstract An analytical method has been developed for the separation of glyoxal (Go), methylglyoxal (MGo), and dimethylglyoxal (DMGo) by MEKC using stilbenediamine (SD) as derivatizing reagent, separation time 6.5,min, SDS as micellar medium at pH,8, and sodium tetraborate (0.1,M) as buffer. Uncoated fused-silica capillary, effective length 50,cm×75,,m id; applied voltage 20,kV and photodiode array detection, were used. Calibration was linear within 0.02,150,,g/mL with detection limits 3.5,5.8,ng/mL. Go and MGo, observed for diabetic and healthy volunteers, were within 0.098,0.193,,g/mL Go and 0.106,0.245,,g/mL MGo with RSD 1.6,3.5 and 1.7,3.4%, respectively, in diabetics against 0.016,0.046,,g/mL Go and 0.021,0.066,,g/mL MGo with RSDs 1.5,3.5 and 1.4,3.6%, respectively, in healthy volunteers. Go and MGo in diabetics were also measured by standard addition and DMGo as an internal standard. Additives do not contribute significantly to Go and MGo matrix. [source] Determination of xanthohumol in hops (Humulus lupulus L.) by nonaqueous CEELECTROPHORESIS, Issue 6 2007Javor Kac Dr. Abstract Xanthohumol (XN) is a prenylated chalcone with antimutagenic and anticancer activity from hops. A nonaqueous reverse polarity capillary electrophoretic method for the determination of XN in hop extract was developed and validated. The optimal parameters were a 64.5,cm long fused-silica capillary with 50,,m id at 25°C; 30,kV negative voltage (anode at detector side of the capillary); nonaqueous buffer with 75,mM NaOH and 50,mM boric acid in methanol; hydrodynamical injection with 10,mbar for 40,s; and detection at 440,nm. XN, isoxanthohumol (IX), colupulone, adlupulone, and n -lupulone were well resolved on the electropherogram. The LOD for XN was 0.05,mg/L and RSD for peak area was below 3%. The amount of XN in different samples of hop pellets varied from 0.14 to 0.42%. [source] Fast CE analysis of adrenergic amines in different parts of Citrus aurantium fruit and dietary supplementsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 16 2010Laura Mercolini Abstract A CE method has been developed for the simultaneous analysis of the adrenergic amines synephrine, octopamine and tyramine in Citrus aurantium (bitter orange) fruit extracts and in dietary supplements. The analytes were separated on a fused silica capillary (50,,m id, 40.0,cm effective length, 48.5,cm total length) using a BGE composed of phosphate buffer (pH 2.5, 50,mM) and applying a 30,kV potential. The samples were injected hydrodynamically at 50,mbar for 25,s. The use of photodiode array detection (,=195,nm) allowed the quantification of the analytes and the control of peak purity. The method has been fully validated, obtaining satisfactory values of precision and extraction yield. The analytes are extracted with water from the dried whole fruits or fruit parts (endocarp, mesocarp and exocarp) or from the commercial formulations and directly injected into the CE apparatus. The results obtained were satisfactory in terms of precision (RSD <,5.7%) and accuracy (recovery >,89%). Thus, the method has demonstrated to be suitable for the qualitative and quantitative determination of synephrine, octopamine and tyramine in C. aurantium extracts, for dietary supplement quality control and for food adulteration identification. [source] Visible light initiated polymerization of styrenic monolithic stationary phases using 470,nm light emitting diode arraysJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2010Zarah Walsh Abstract Poly(styrene- co -divinylbenzene) monolithic stationary phases have been synthesized for the first time by photoinitiated polymerization. An initiator composed of (+)-(S)-camphorquinone/ethyl-4-dimethylaminobenzoate/N- methoxy-4-phenylpyridinium tetrafluoroborate was activated using a 470,nm light emitting diode array as the light source. Spatially controlled polymerization of styrenic monoliths has been achieved within specific sections of a 100,,m id polytetrafluoroethylene-coated fused-silica capillary using simple photo masking. The sharpness of the edges was confirmed by optical microscopy, while SEM was used to verify a typical porous, globular morphology. Flow resistance data were used to assess the permeability of the monoliths and they were found to have good flow through properties with a flow resistance of 0.725,MPa/cm at 1,,L/min (water, 20°C). Conductivity profiling along the length of the capillary was used to assess their lateral homogeneity. Monoliths which were axially rotated during polymerization were found to be homogeneous along the whole length of the capillary. The monolithic stationary phases were applied to the RP gradient separation of a mixture of proteins. Column fabrication showed excellent reproducibility with the retention factor (k) having a RSD value of 2.6% for the batch and less than 1.73% on individual columns. [source] Alkylated poly(styrene-divinylbenzene) monolithic columns for ,-HPLC and CEC separation of phenolic acidsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2007Zdenka Ku, erová Abstract Macroporous poly(styrene-divinylbenzene) monolithic columns were prepared in fused silica capillaries of 100 ,m id by in-situ copolymerization of styrene with divinylbenzene in the presence of propan-1-ol and formamide as the porogen system. The monoliths were subsequently alkylated with linear alkyl C-18 groups via Friedel-Crafts reaction to improve the retention and chromatographic resolution of strongly polar phenolic acids. A new thermally initiated grafting procedure was developed in order to shorten the time of the alkylation process. The grafting procedure was optimized with respect to the reaction temperature, time, the grafting reactant concentration, and the solvent used. The type of solvent and the grafting temperature are the most significant factors affecting the hydrodynamic properties, porosity, and efficiency of the columns. While the equivalent particle diameter of the grafted column increased, the capillary-like flow-through pore diameter decreased in comparison to non-alkylated monoliths. The hydrodynamic permeability of the monolith decreased, but the monolithic column still permitted fast ,-HPLC separations. [source] | ||||||||||