Browsing by Author "Yu, Tiing"

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Counter-current chromatography using hexane/surfactant-containing water solvent systems
(2006-08-04)
Shen, Ching-Wei
;
Boon, Siew-Keem
;
Chang, Yu-Pei
;
Yu, Tiing
;
應用化學系
We developed a n-hexane/surfactant-containing water solvent system in counter-current chromatography (CCC) in order to separate hydrophobic compounds. By using the upper phase as the mobile phase, we have separated steroid samples. Retention times of steroids progesterone and Delta(4)-androstene-3,17-dione increased slightly by increasing the concentration below the critical micellar concentration (CMC) of surfactant sodium 1-heptanesulfonate. However, the retention times increased drastically while the SHS concentrations were above the CMC. The partition of these two steroids in the two phases was significantly dependent on the interaction with micelles. Aromatic hydrocarbons were not retained by the lower phase no matter what the surfactant concentrations were. Their hydrophobic interaction with n-hexane greatly exceeded that with the micellar solution. The retention times of esters, however, were only slightly affected by the surfactant addition even above the CMC. The weaker interaction between esters and the micellar solution was probably due to their higher polarity. The micellar solvent systems provide an alternative way for hydrophobic sample separations in CCC, but the performance is limited. (c) 2006 Published by Elsevier B.V.
Dispersion-convolution model for simulating peaks in a flow injection system
(2007-01-12)
Pai, Su-Cheng
;
Lai, Yee-Hwong
;
Chiao, Ling-Yun
;
Yu, Tiing
;
應用化學系
A dispersion-convolution model is proposed for simulating peak shapes in a single-line flow injection system. It is based on the assumption that an injected sample plug is expanded due to a "bulk" dispersion mechanism along the length coordinate, and that after traveling over a distance ora period of time. the sample zone will develop into a Gaussian-like distribution. This spatial pattern is further transformed to a temporal coordinate by a convolution process, and finally a temporal peak image is generated. The feasibility of the proposed model has been examined by experiments with various coil lengths, sample sizes and pumping rates. An empirical dispersion coefficient (D*) can be estimated by using the observed peak position. height and area (t(p)(*), h* and A(t)(*)) from a recorder. An empirical temporal shift ((Phi*) can be further approximated by (Phi* = D*/u(2), which becomes an important parameter in the restoration of experimental peaks. Also, the dispersion coefficient can be expressed as a second-order polynomial function of the pumping rate Q, for which D*(Q) =delta(0) + delta(1)Q+delta(2)Q(2). The optimal dispersion occurs at a pumping rate of Q(opt) = root delta(0)/delta(.)(2) This explains the interesting "Nike-swoosh" relationship between the peak height and pumping rate. The excellent coherence of theoretical and experimental peak shapes confirms that the temporal distortion effect is the dominating reason to explain the peak asymmetry in flow injection analysis. (c) 2006 Elsevier B.V. All rights reserved.
Examination of the temporal effect in a flow injection analysis system using multi-channel absorbance detection
(2009-05-22)
Lin, Shu-Hui
;
Chang, Kai-Chieh
;
Chen, Yu-Chun
;
Yu, Tiing
;
Pai, Su-Cheng
In addition to the Poiseuille effect, a so-called temporal effect was proposed recently to elucidate the commonly observed tailing peak signals of flow injection analysis (FIA). A multi-channel absorbance detector was used in this study to obtain the FIA peaks on both the spatial and temporal coordinates. The temporal effect was analyzed by comparison of the profiles between the experimental and the corresponding Gaussian peaks. and by comparison of asymmetry factors between the spatial and the temporal peaks. The temporal effect appeared to be the major factor under flow rates ranging from 0.5 to 8 ml min(-1). This was despite the presence of a spatially frontal peak observed in the FIA tubing, which was found to result in a tailing peak on the temporal coordinate due to this discussed cause. in addition, the temporal effect became greater as the flow rate increased. (C) 2009 Published by Elsevier B.V.
Interpretation on Band-broadening in Chromatography with Spatial Peak Profiles Obtained Using Whole-column Detection
(2009-06-01)
Lin, Shu-Hui
;
Yu, Tiing
;
Pai, Su-Cheng
;
應用化學系
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Department of Applied Chemistry
Fifteen liquid chromatographic experiments were investigated using a whole-column detection (WCD) system and a conventional post-column UV/Vis detector. The peak widths obtained from chromatograms were found dependent on the retention factor; the larger the retention factor was the greater the peak width. However, the on-column spatial peak widths were dependent on the locations where they were measured in the column. The peak widths monitored at 17 cm from the column inlet were found essentially the same no matter what their retention factors were. In addition, a linear relationship was found between the chromatographic peak width and the reciprocal of the average linear rate of the solute migration. The peak widths on chromatograms did not reflect how they appeared in the column; instead, the widths were determined by the solute speed passing the detector.
Liquid-liquid extraction of lysozyme using a dye-modified ionic liquid
(2008-06-06)
Tzeng, Yu-Ping
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Shen, Ching-Wei
;
Yu, Tiing
;
應用化學系
;
Department of Applied Chemistry
An affinity-dye, Cibacron Blue 3GA (CB), derivatized organic salt [BMIM](3)[CB] was synthesized for lysozyme extraction. This compound was formed by mixing an ionic liquid (IL) [BMIM][CI] and the silver salt of CB. Liquid-liquid extractions of lysozyme from the aqueous and [BMIM](3)[CB] in [BMIM][PF6] solutions were examined in this study. The transfer of lysozyme from the aqueous phase to the IL phase decreased while the pH of the aqueous phase increased. An extraction higher than 90% was observed at pH 4. Under a high ionic strength, the lysozyme would transform back from the IL phase into the aqueous phase. Lysozyme molecules were almost quantitatively recovered from the IL phase to the aqueous solutions of 1 M KCl under pH 9-11. It appeared that the extraction was specific for lysozyme in contrast to cytochrome c, ovalbumin, and bovine serum albumin. The extraction efficiency of the IL phase remained essentially the same after eight cycles of extraction. (c) 2008 Elsevier B.V. All rights reserved.
Peak crossover in high-performance liquid chromatography elution monitored using whole-column detection
(2008-08-01)
Lin, Shu-Hui
;
Yu, Tiing
;
Sheu, Alf
;
Yang, Der-Jyh
;
Pai, Su-Cheng
A whole-column detection (WCD) system was fabricated using the parts from a typical A4 size optical scanner. Optimum layout of the fluorescence tube, beam condenser and photon transducers from the scanner made an effective devise to examine the dynamic chromatographic separation process. This system was applied in monitoring peak crossover in an ion-pair chromatographic elution. A stage-wise gradient was conducted in eluting a mixture of New Coccine and Carmoisine. Compound New Coccine lagging behind after sample injection moved passing Carmoisine at the column outlet. The complete on-column elution process could be observed directly using this detection system. This inexpensive and rugged WCD system provided a 0.3 mm spatial resolution and a 3.6 ms temporal resolution and was proven to be an adequate device to directly monitor solute retention behavior in the liquid chromatography column. (c) 2008 Elsevier B.V. All rights reserved.
Peak shape and dispersion behavior of solutes in counter-current chromatography with a single phase
(2009-10-02)
Shen, Ching-Wei
;
Yu, Tiing
;
應用化學系
;
Department of Applied Chemistry
The dispersion behavior of solutes was investigated in a rotating flowing coiled tube. Potassium iodide, tartrazine, ascorbic acid, lysozyme, bovine serum albumin (BSA), and silver nanoparticle (AgNPs) samples were eluted in a coiled tube of counter-current chromatography (CCC) apparatus with a single phase. Apparent convection peaks of low-diffusivity Solutes appeared in the static CCC tube, while Gaussian-like peaks showed Up for the high-diffusivity solutes. When the rotation speed of the CCC apparatus was elevated, all solute peak widths became smaller, and the convection peaks of AgNPs and BSA were minimized and formed Gaussian-like peaks. The axial dispersions of all solutes were reduced owing to the higher radial mass transfer in the rotating CCC column. The same reasoning could also be used to rationalize other special band shapes encountered in two-phase CCC separations. (C) 2009 Elsevier B.V. All rights reserved.
Protein separation and enrichment by counter-current chromatography using reverse micelle solvent systems
(2007-06-01)
Shen, Ching-Wei
;
Yu, Tiing
;
應用化學系
;
Department of Applied Chemistry
A protein mixture consisting of myoglobin, cytochrome c, and lysozyme was separated by high-speed counter-current chromatography using a two-phase aqueous/reverse micelle-containing organic solvent system. About 50% stationary phase retention ratio was obtained in most chromatographic experiments. Separations were manipulated mainly by pH gradients that controlled the electrostatic interactions between the protein molecules and reverse micelles. Separations were further improved by incorporating an ionic strength gradient along with the pH gradient. Control of ionic strength in the aqueous solution helped fine-tune protein partitioning between the stationary and mobile phases. Although non-specific protein interactions affected baseline resolution, recovery of cytochrome c and lysozyme reached 90% and 82%. Furthermore, concentration or enrichment of these two proteins was achieved from a large-volume sample load. This technique can potentially be employed in the recovery and enrichment of proteins from large-volume aqueous solutions. (C) 2007 Elsevier B.V. All rights reserved.
Size-fractionation of silver nanoparticles using ion-pair extraction in a counter-current chromatograph
(2009-08-07)
Shen, Ching-Wei
;
Yu, Tiing
;
應用化學系
;
Department of Applied Chemistry
Size separation of silver nanoparticles was investigated in counter-current chromatography (CCC) based on a unique step-gradient extraction process. Carboxylate anions were modified on silver nanoparticles to produce water-dispersible nanoparticles. The aqueous nanoparticles were readily transferred to the organic phase (toluene/hexane = 1: 1, v/v) together with the phase transfer catalyst, tetraoctylammonium bromide (TOAB), owing to the ion-pair adduct formation between silver nanoparticle anions and tetraoctylammonium cations. Smaller nanoparticles were found to be more readily transferred to the organic phase compared to larger nanoparticles. Various concentrations of TOAB in the organic elution phase were used in the CCC extraction experiments. it appeared that a concentration of 0.02 mM of TOAB was adequate to achieve optimum separation and recovery for the aqueous Ag nanoparticle sample (1.5 mg) in the CCC extraction experiments. Samples of 15.8 +/- 5.3 nm were separated; the distributions of four fractions collected were 13.7 +/- 1.9, 14.1 +/- 3.5, 19.2 +/- 4.3, and 22.2 +/- 4.9 turn. Compared with the step-wise extraction performed in this study, the step-gradient extractions using CCC provided much better size discrimination. (C) 2009 Elsevier B.V. All rights reserved.
Solubility measurements of surfactants and dissolution of cytochrome c in 1,1,1,2-tetrafluoroethane modified with organic solvents
(2007-02-01)
Li, Jie-Ren
;
Yu, Tiing
;
應用化學系
;
Department of Applied Chemistry
The solubilities of four surfactants, sodium bis-2-ethylhexyl sulfosuccinate (AOT), cetyltrimethylammonium chloride, didodecyldimethylammonium bromide, and n-dodecyltrimethylammonium chloride in liquid refrigerant 1,1,1,2-tetrafluoroethane (R134a) modified with methanol, ethanol, and 2-propanol were measured. The measurements were performed under 25 and 50 bar at 25 degrees C. The solubility of AOT was as high as 92 mM in R134a with addition of 2% ethanol. Cytochrome c molecules were then verified to be soluble in the AOT-containing and ethanol-modified R134a solution. Accordingly, liquid R134a is suggested as a potential extraction solvent for hydrophilic compounds.