Browsing by Author "Yu, T"

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Analysis of acidic herbicides in water using a toroidal coil CCC
(2003)
Huang, YL
;
Yu, T
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應用化學系
;
Department of Applied Chemistry
A newly developed compact toroidal coil centrifuge chromatograph (TCCC) has been proven to be able to achieve high-resolution counter-current chromatography (CCC) separations. The potential of this devise is studied for analytical applications. The TCCC was used for the analysis of acidic herbicides in order to reduce the interference due to humic substances. Aqueous samples were pretreated with solid-phase extraction (SPE) and eluted with the lower phase of an n-hexane-ethyl acetate-water (15: 7: 20, v/v/v) solvent system. Because the humic substances were more hydrophilic than the herbicides, they were eluted first and separated from the herbicides. Although four herbicides were well resolved,. quantification of compound 2,4-dichloro-phenoxyacetic acid was, to some extent affected by the tailing signal of humic substances. Samples of analytes of 20 mug/L spiked in deionized water containing 6 and 12 mg/L humic acid, and in lake water, were analyzed. Mean recoveries ranged between 66 and 96%, with RSDs between 2 and 11%. While CCC has been known as a preparative chromatographic technique, the potential of using a TCCC device for quantitative analysis under complex matrices is demonstrated.
Correlation of supercritical fluid extraction with supercritical fluid chromatography in aqueous matrixes
(1998-05-15)
Yu, T
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Luo, SK
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Chen, SJ
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應用化學系
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Department of Applied Chemistry
A mathematical model is presented for correlating supercritical fluid chromatography (SFC) in aqueous stationary phases with supercritical fluid extraction (SFE) in aqueous matrixes. A solar coaxial countercurrent chromatography apparatus was used for the SFC and SFE experiments. The SFE extraction vessel, i.e., the column for SFC, was mathematically divided into limited layers. During extraction, each layer was considered to undergo a chromatographic process. The plate heights of all the layers were regarded equal throughout the column because pressure drops in the system were negligible. Each layer's chromatographic capacity factor and peak width were calculated using true SFC experimental data, and the sum of all these peak distributions as a function of time gave the extraction efficiency. Accordingly, the SFE analyte recovery curve could be simulated using SFC data and this model. Since SFC operations are more straightforward than SFE operations, SFE optimization may be more easily achieved using this mathematical correlation. The simulated analyte data of large capacity factors matched the experimental results very well. Deviations gradually became greater as analyte capacity factors were decreased. A rationale is proposed that satisfactorily interprets this deviation trend.
Counter-current chromatography using supercritical fluid carbon dioxide as mobile phase
(1996-02-16)
Yu, T
;
Li, SE
;
Chen, YH
;
Wang, HP
;
應用化學系
Supercritical fluid carbon dioxide was employed in solar eccentric counter-current chromatography (SECCC) to replace the liquid mobile phase in the traditional arrangement. The fundamental difference from the conventional liquid-liquid system is the requirement for high-pressure operation. The experimental set-up is presented to illustrate the necessary modifications that accommodate operation with a supercritical fluid. Studies on the stationary phase retention due to various experimental conditions are discussed. A mixture of acetophenone and benzophenone was chromatographed using mixtures of water and methanol as the stationary solvent system to demonstrate the feasibility of this technique. At present the efficiency of the separation is not satisfactory owing to the phase separator inserted in the system to remove liquid droplets which contributed to considerable peak broadening.
Measurements of partition coefficients in water-1,1,1,2-tetrafluoroethane by countercurrent chromatography
(2001)
Yu, T
;
Chang, JY
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應用化學系
;
Department of Applied Chemistry
Recently, refrigerant 1, 1, 1, 2 -tetrafluoro ethane (R134a) was considered as an extraction solvent alternative to supercritical fluid CO2. We measured water-liquid R134a partition coefficients of some organic compounds using a high-speed countercurrent chromatography (HSCCC). The experiment could be operated by moderate modification of the commercial instrument. The partition coefficient data were obtained under 15 degrees, 25 degrees, and 45 degreesC.
Resolution studies on counter-current chromatography using supercritical fluid carbon dioxide
(1997-11-28)
Yu, T
;
Chen, YH
;
應用化學系
;
Department of Applied Chemistry
Counter-current chromatography (CCC) is a form of Liquid-liquid partition chromatography. It requires two immiscible solvent phases; the stationary phase is retained in thr separation column, generally by centrifugal force, while the mobile phase is eluted. We recently replaced the mobile phase with supercritical fluid carbon dioxide (SF CO2). Since the solvent strength of SF CO2 can be varied by changing the temperature and pressure of the system, separation adjustments are thus more versatile. We investigated the pressure and temperature effects on resolution using water and low-carbon alcohol mixtures as the stationary phases. It was demonstrated that these special properties of SF CO2 were indeed beneficial to the optimization of separations. In addition, the phase retention ratio was examined in terms of separation resolution. The results appeared very similar to those obtained from conventional traditional CCC. This study should be helpful for the future development of SF applications in CCC. (C) 1997 Elsevier Science B.V.
Resolution studies on counter-current chromatography using supercritical fluid carbon dioxide
(1997-11-28)
Yu, T
;
Chen, YH
;
應用化學系
;
Department of Applied Chemistry
Counter-current chromatography (CCC) is a form of Liquid-liquid partition chromatography. It requires two immiscible solvent phases; the stationary phase is retained in thr separation column, generally by centrifugal force, while the mobile phase is eluted. We recently replaced the mobile phase with supercritical fluid carbon dioxide (SF CO2). Since the solvent strength of SF CO2 can be varied by changing the temperature and pressure of the system, separation adjustments are thus more versatile. We investigated the pressure and temperature effects on resolution using water and low-carbon alcohol mixtures as the stationary phases. It was demonstrated that these special properties of SF CO2 were indeed beneficial to the optimization of separations. In addition, the phase retention ratio was examined in terms of separation resolution. The results appeared very similar to those obtained from conventional traditional CCC. This study should be helpful for the future development of SF applications in CCC. (C) 1997 Elsevier Science B.V.
Separation of steroids by countercurrent chromatography using supercritical fluid carbon dioxide
(1999)
Yeh, CS
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Yu, T
;
Berthod, A
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應用化學系
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Department of Applied Chemistry
Since the introduction of the modem apparatus and technology of countercurrent chromatography (CCC), researchers have found numerous applications in the analyses and preparations of natural products. Selection of appropriate solvent systems is a basic and important task for separation in CCC. Recently, we provided an alternative choice of the solvent system by replacing the liquid mobile phase with supercritical-fluid carbon dioxide (SFCO2). In this work, three steroids - progesterone, Delta(4)-androstene-3,17-dione, and (+)-4-cholesten-3-one were separated as test compounds using SFCO2 as the mobile phase and methanol-water (30/70 v/v) solution as the stationary phase.
Solubilization of hydrophilic compounds in 1,1,1,2-tetrafluoroethane with a cationic surfactant
(2000-03-15)
Li, JR
;
Lee, YM
;
Yu, T
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應用化學系
;
Department of Applied Chemistry
Solubilization of hydrophilic compounds was examined in liquid 1,1,1,2-tetrafluoroethane (R134a) in the presence of the cationic surfactant trioctylmethylammonium chloride (TOMAC). The absorption spectra of methyl orange in the TOMAC-containing R134a solutions were obtained. Significant blue shifts were observed in comparison with the spectrum of methyl orange in aqueous solution. The shifts decreased as the water-to-surfactant ratio, Wb, increased. In addition, spectral measurements confirmed the dissolution of cytochrome c in R134a in the presence of TOMAC. R134a remains as a liquid under mild applied pressure and becomes gas under ambient conditions; it therefore separates from analytes of interest directly without further concentration when used as an extraction solvent. Accordingly, it may be applied to recover valuable hydrophilic substances of low concentration from aqueous solutions.
Suppressing tumor progression and inducing cell differentiation on prostate cancer cells by human psychosomatic power
(2002-03-20)
Yu, T
;
Hwang, ML
;
Tsai, WL
;
Sheu, JJC
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應用化學系
Suppressing tumor progression of in vitro prostate cancer cells by emitted psychosomatic power through Zen meditation
(2003)
Yu, T
;
Tsai, HL
;
Hwang, ML
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應用化學系
;
Department of Applied Chemistry
Human prostate cancer PO cells were treated in vitro with psychosomatic power emitted by a Buddhist-Zen Master. A significant decrease of growth rate was observed as determined by MTT assay after 48 hours. These cells also had two- to three-fold higher levels of prostatic acid phosphatase (PAcP) activity, a prostate tissue-specific differentiation antigen. In addition, the treated cells formed fewer and smaller colonies in soft agar as compared with control cells, which displayed anchorage-independent growth. These observations provide insight into the suppressive effects of healing power through the practice of Buddhist-Zen meditation on tumor progression. The emitted bioenergy may be suggested as an alternative and feasible approach for cancer research and patient treatment. Keywords: Cancer; Complementary and Alternative Medicine;