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Short Column (short + column)
Selected AbstractsSynthesis of cyclodextrin-based polymers and their use as debittering agentsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Arianna Binello Abstract Cyclodextrins (CDs) and their derivatives are used to suppress unpleasant tastes and odors or to achieve a controlled release of certain food constituents. This article describes the synthesis by nonconventional methods of (1) crosslinked, insoluble CD polymers and (2) water-soluble, CD-grafted carboxymethylchitosan and carboxymethylcellulose. The CD polymers were obtained by the reaction of ,-CD with one of the following crosslinking agents: epichlorohydrin, diphenyl carbonate, or hexamethylene diisocyanate. Their preparations were usually carried out under high-intensity ultrasound, which resulted in much shorter reaction times and narrower distributions of particle size (as determined by scanning electron microscopy measurements). A novel, insoluble CD polymer was obtained by reticulation under microwaves of propargyl-,-CD with 1,3-bis(azidomethyl)benzene through Huisgen 1,3-dipolar cycloaddition. Short columns packed with the insoluble polymers were found to efficiently sequester naringin from aqueous solutions; successively, they could be easily regenerated by a counter-current ethanol wash that also achieved an excellent recovery of the flavonoid. Differential scanning calorimetry thermograms showed that the crosslinked CD polymers formed inclusion complexes with naringin. The soluble polymers also interacted with bitter flavonoids of citrus fruits (naringin and limonin), as shown by the results of sensorial panel tests, in which they behaved as bitter-masking agents. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Characterization of Taylor vortex flow in a short liquid columnAICHE JOURNAL, Issue 12 2009Rensheng Deng Abstract We present a study on Taylor vortex flow in the annulus between a rotating inner cylinder and a stationary outer cylinder, featured with a wide gap (radius ratio is 0.613) and a short column (aspect ratio is 5.17). A particle image velocimetry (PIV) system was used to determine the position, shape, and velocity distribution of the vortices, by which the flow was also confirmed to lie in the nonwavy Taylor vortex regime for all operating conditions explored in this study. Our results suggest that end boundary effects are important, in which the vortex number decreases with decreasing column length. For a system with an aspect ratio of 5.17, six vortices appear in the gap with their position, size, and shape varying at different Reynolds numbers. The fluid velocities show an asymmetric feature with respect to the vortex centers, while the maximum axial and radial velocities increase almost linearly with the increasing reduced Reynolds number (Re , Rec). In addition, computational fluid dynamics study was employed under the same conditions, and its results agree well with the PIV measurements. Overall, this study provides a quantitative understanding of the formation of Taylor vortices in a constrained space. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Pyrazole functionalized organo-ceramic hybrids for noble metal separationsAICHE JOURNAL, Issue 10 2005Jun S. Lee Abstract A series of pyrazole-functional adsorbents is synthesized by sol,gel processing technology and used to study the extraction characteristics for palladium, platinum, and gold chlorides from leaching solutions. An organosilicon compound, N-(trimethoxysilylpropyl)-pyrazole, is synthesized as the functional precursor for these adsorbents. Hydrothermal treatments for the gelled materials alter pore characteristics without chemical property changes. To study adsorptive extraction of Pd(II), Pt(IV), and Au(III) chlorides, the hydrothermally treated adsorbent is used. The experimental results show that this adsorbent has high Pd(II) uptake capacity (1.41 mmol/g), strong selectivity for Pd(II) chloride over Pt(IV) and Au(III) chlorides, and no reactivity for Cu(II) and Fe(II) in 2.0 M HCl solutions. The material also has sustainable stability over repeated metal loading and stripping in a short column. In addition to the experimental studies, the adsorption processes in batch and packed column systems are successfully modeled by using a pore diffusion model and presented. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source] Micellar and aqueous-organic liquid chromatography using sub-2,,m packings for fast separation of natural phenolic compoundsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2010Jun Cao Abstract The objective of the present work was to investigate the chromatographic behavior of natural phenolic compounds in micellar and aqueous-organic LC using a short column packed with 1.8,,m particles. Firstly, the effect of ACN and SDS on elution strength and selectivity was examined by isocratic submicellar (0,30% ACN/5% 1-butanol/1,6,mM SDS) and micellar (0,30% ACN/5% 1-butanol/40,60,mM SDS) systems. The varied concentrations of two modifiers in the mobile phases revealed different eluting power. Then, the application of organic modifier gradient was discussed in both submicellar and micellar LC using mobile phases of 4,mM SDS/5% 1-butanol or 50,mM SDS/5% 1-butanol containing ACN gradient from 0 to 30%, respectively. For micellar system, the separation was found to be better in gradient than isocratic elution. Additionally, the sensitivity of aqueous-organic LC was examined. The mobile phase was a mixture of ACN and water employing gradient elution at a flow rate of 0.5,mL/min, with analysis time below 9,min. It was found that separation efficiency was significantly better compared with micellar LC. Besides, the aqueous-organic LC has been applied to separation of various phenolic compounds in Yangwei granule or Radix Astragali samples. [source] High-speed separation and characterization of major constituents in Radix Paeoniae Rubra by fast high-performance liquid chromatography coupled with diode-array detection and time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 1 2009E-Hu Liu A fast high-performance liquid chromatography (HPLC) method coupled with diode-array detection (DAD) and electrospray ionization time-of-flight mass spectrometry (ESI-TOFMS) has been developed for rapid separation and sensitive identification of major constituents in Radix Paeoniae Rubra (RPR). The total analysis time on a short column packed with 1.8-µm porous particles was about 20,min without a loss in resolution, six times faster than the performance of a conventional column analysis (115,min). The MS fragmentation behavior and structural characterization of major compounds in RPR were investigated here for the first time. The targets were rapidly screened from RPR matrix using a narrow mass window of 0.01,Da to restructure extracted ion chromatograms. Accurate mass measurements (less than 5,ppm error) for both the deprotonated molecule and characteristic fragment ions represent reliable identification criteria for these compounds in complex matrices with similar if not even better performance compared with tandem mass spectrometry. A total of 26 components were screened and identified in RPR including 11 monoterpene glycosides, 11 galloyl glucoses and 4 other phenolic compounds. From the point of time savings, resolving power, accurate mass measurement capability and full spectral sensitivity, the established fast HPLC/DAD/TOFMS method turns out to be a highly useful technique to identify constituents in complex herbal medicines. Copyright © 2008 John Wiley & Sons, Ltd. [source] Simultaneous determination of triptolide, tripdiolide and tripterine in human urine by high-performance liquid chromatography coupled with ion trap atmospheric-pressure chemical ionization mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 3 2009Mi-cong Jin Abstract An accurate and selective method for the simultaneous determination of triptolide, tripdiolide and tripterine in human urine using hydrocortisone as an internal standard (IS) by high-performance liquid chromatography coupled with atmospheric-pressure chemical ionization mass spectrometry in negative ion mode has been developed. After triptolide, tripdiolide and tripterine in human urine were extracted with ethyl acetate and cleaned by solid-phase extraction with C18 cartridges, a satisfactory separation was achieved on an XDB C18 short column (30 × 2.1 mm i.d., 3 µm) using the mobile phase of acetic acid,ammonium acetate (5 mmol/L, pH = 4.5),acetonitrile,methanol in gradient elution. Detection was operated by APCI in selected ion monitoring mode. The target ions m/z 359, m/z 375, m/z 449 and m/z 419 were selected for the quantification of triptolide, tripdiolide, tripterine and IS, respectively. The linear range was 1.0,100.0 ng mL,1, and the limits of quantification in human urine were found to be 0.1,0.5 ng mL,1 for the three compounds. The precisions (CV%) and accuracies were 6.6,12.9 and 85.1,97.0%, respectively. The developed method could be applied to the determination of triptolide, tripdiolide and tripterine in human urine for diagnosis of the intoxication and for forensic purposes. Copyright © 2008 John Wiley & Sons, Ltd. [source] Separation, optimization, miniaturization and signal space.JOURNAL OF CHEMOMETRICS, Issue 4 2009Optimum measurability factors in process analytical chromatography Abstract The theory concerning optimum separation conditions with respect to the precision and minimum peak estimation error is extended with the derivation of the conditions for optimum measurability in case of chemical process control, resulting in extremely short columns to be used. High-speed correlation chromatography (CC) with a special input device is suggested as a solution for the practical problems of these required columns. An example of a one-second correlogram with a spark modulation input device is shown. An alternative is monitoring chemical processes by multiple input chromatography, applying a polynomial fit procedure. Copyright © 2009 John Wiley & Sons, Ltd. [source] Fundamental and practical aspects of ultrahigh pressure liquid chromatography for fast separationsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 8 2007Naijun Wu Abstract The ongoing development of HPLC has been focused on increasing the speed and efficiency of separations over the past decade. The advances in separation speed have been primarily related to the development of column technology and instrumentation. Relatively short columns packed with sub-2 ,m particles provide high-speed separations while maintaining or increasing resolution. Ultrahigh pressure pump systems have been developed to overcome the high-pressure drop generated by such sub-2 ,m packings. In this review, fundamental and practical aspects of ultrahigh pressure or ultrahigh performance liquid chromatography (U-HPLC) are discussed. Applications of fast U-HPLC separations are also presented. [source] Fast analysis in liquid chromatography using small particle size and high pressureJOURNAL OF SEPARATION SCIENCE, JSS, Issue 12 2006Dao T.-T. Abstract In order to enhance chromatographic performances in terms of efficiency and rapidity, LC has recently evolved in the development of short columns packed with small particles (sub-2 ,m) working at high pressures (>400 bar). This approach has been described 30 years ago according to the fundamental chromatographic equations. However, systems and columns compatible with such high pressures have been introduced in the market in 2004 only. Advantages of small particles working at high pressure will be discussed in terms of sensitivity, efficiency, resolution, and analysis time. Potential problems encountered with high pressure in terms of frictional heating and solvent compressibility will also be discussed even if systems working at a maximum pressure of 1000 bar are not influenced by these parameters and give reliable and reproducible results. Several applications will highlight the potential and interest of this new technology. [source] | ||||||||||