Yw Lee

Dual Countercurrent Chromatography

Abstract A modern method of performing conventional countercurrent distribution called Dual Countercurrent Chromatography is described. The system consists of a multilayer coiled column integrated with two inlet and two outlet lines for solvent phases and a sample feed line. Subjecting the system to a particular combination of centrifugal and planetary motions produces a unique hydrodynamic effect which allows two immiscible liquids to flow countercurrently through the coiled column. The sample solution is fed at the middle portion of the column and eluted simultaneously through the column in the opposite direction by two liquids. This distinct feature of maintaining a constant fresh two phases within the coiled column permits a rich domain of application, such as continuous sample process and continuous extraction. The present paper describes the application of this dual countercurrent system to the separation of natural products and synthetic intermediates. Preliminary results indicate that this new met...

Application of Countercurrent Chromatography/Thermospray Mass Spectrometry for the Analysis of Natural Products

Abstract The versatility and high resolving power of countercurrent chromatography (CCC) has been demonstrated with a newly developed analytical high speed planet centrifuge system. Interfacing countercurrent chromatography with mass spectrometry (MS) provides a new analytical methodology which integrates the advantages of countercurrent chromatography with the low detection limit and identification capability of mass spectrometry. The capability of thermospray CCC/MS is evidenced in a preliminary study of plant alkaloids. The technique proved useful in identifying an unknown impurity and in validating the presence of a specific compound in a mixture. The thermospray CCC/MS can become a useful and complementary method to thermospray HPLC/MS for the analysis of nonvolatile or thermally unstable molecules.

Purification of Uridine Phosphorylase from Crude Extracts of Escherichia Coli Employing High-Speed Countercurrent Chromatography With an Aqueous Two-Phase Solvent System

Abstract This is a preliminary report on a novel liquid-liquid parti tioning chromatography method for the purification of recombinant protein, uridine phosphorylase (UrdPase). This system utilizes an aqueous two-phase solvent system, consisting of polyethylene glycol and phosphate buffer, with a newly developed high-speed countercurrent centrifuge (X-axis, XLL type). The system is capable of purifying crude recombinant UrdPase in an efficient manner.

Application of High Speed Countercurrent Chromatography/Thermospray Mass Spectrometry for the Analysis of Bio-Active Triterpenoic Acids from Boswellia Carterh

Abstract The versatility and high resolving power of countercurrent chromatography has been demonstrated with a newly developed analytical high speed planet centrifuge system (HSCCC). Interfacing countercurrent chromatography with mass spectrometry (MS) provides a new analytical methodology which Integrates the advantages of countercurrent chromatography with the low detection limit and identification capability of mass spectrometry. The capability of thermo-spray HSCCC/MS has been successfully demonstrated in the identification of plant alkaloids and lignans. In this paper, the technigue proved useful in identifying and validating the bio-active and structural closely related triterpenoid carboxylic acids from a crude extract of Boswellia carterii (Burseraceae). Thermospray HSCCC/MS can become a useful and complementary method to thermospray HPLC/MS for the analysis of nonvolatile or thermally unstable molecules.

Analytical High Speed Countercurrent Chromatography

Abstract The resolution of countercurrent distribution has long been demonstrated. However, the long elution time limits its analytical applications. The development of a high speed planet centrifuge has markedly improved the efficiency of the system; thus the countercurrent chromatography can be completed within several hours instead of days. Further reduction in separation time is still needed for analytical use, however. The most effective approach to improve the efficiency is to use a smaller diameter tubing for the multilayer coiled column, because it provides for better phase mixing. Under standard operation conditions, the increased phase interaction has resulted in steady carry-over of the stationary phase. This was solved with a high revolutional speed which provides the necessary centrifugal force for sustaining the stationary phase. Excellent phase retention and resolution have been achieved with a 0.85 mm i.d. column and a 2000 rpm revolutional speed. The analytical capability of the new syste...

Dual counter-current chromatography —its applications in natural products research

Abstract Dual counter-current chromatoraphy is a newly developed separation method which allows the performance of classic counter-current distribution in a highly efficient manner. The principles of CCC and its capabilities, as illustrated by several applications in natural products isolations, are reviewed.

Improved High-Speed Countercurrent Chromatograph with Three Multilayer Coils Connected in Series. III. Evaluation of Semianalytical Column with Various Biological Samples and Inorganic Elements

Abstract The partition efficiency of the counter-current chromatographic centrifuge was improved by mounting a set of three multilayer coils prepared from a 1.07 mm I.D. and ca 300 m length of PTFE (polytetrafluoroethylene) tube with a total capacity of 270 ml. The high performance of the present apparatus has been successfully demonstrated in separations of various testing samples which include DNP (dinitrophenyl) amino acids, indole auxins, tetracycline derivatives, flavonoids, bacitracin, triterpenoic acids, and lanthanoid chlorides.

Preparative Separation of Demeton Isomers with Ito Multi-Layer Coil Countercurrent Chromatography

Abstract The active constituents of the insecticide Demeton, consisting of isomeric 0, 0-diethyl (O, S)-ethylmercaptoethyl thiophosphates, have been conveniently separated on a preparative scale with an Ito multi-layer coil countercurrent system.