Dual Counter-current Chromatography Research Articles

Developments in high-speed countercurrent chromatography and its applications in the separation of terpenoids and saponins.

High-speed countercurrent chromatography is a liquid-liquid separation chromatographic technique, which has the unique feature of eliminating irreversible adsorption using liquid support medium, and is widely used in research and development of traditional Chinese medicine, biochemistry, food, environment analysis, and so on. In this review, some new developments of countercurrent chromatography, for instance cross-axis countercurrent chromatography, dual countercurrent chromatography, foam countercurrent chromatography, and pH-zone-refining countercurrent chromatography are presented. Furthermore, the research and progress in high-speed countercurrent chromatography techniques and its application in the separation and purification of terpenoids and saponins are reviewed.

Counter-Current Chromatography for High Throughput Analysis of Natural Products

Counter-current chromatography (CCC) is a unique support-free liquid-liquid partition chromatography winning wide applications in the separation of various components from natural or synthetic mixtures. It has been one of the prime methods for isolating compounds from Traditional Chinese Medicines (TCM) and other comprehensive natural products. Although early CCC models produced a long-standing false image that CCC is a time-consuming technique, rapid and high-performance CCC devices and methods for high-throughput analysis of natural mixtures have been advanced. For instances, multi-channel CCC, dual CCC, elution-extrusion CCC, and solvent simplification protocols can provide high-throughput CCC analysis and produce high purity of compounds or large natural product libraries for drug discovery. This review summarizes the recent advancements of CCC in the high-throughput analysis of natural product with an emphasis on the developments of instruments and methods.

Mathematical model of computer-programmed intermittent dual countercurrent chromatography applied to hydrostatic and hydrodynamic equilibrium systems

Dual high-speed countercurrent chromatography (dual CCC) literally permits countercurrent flow of two immiscible solvent phases continuously through the coiled column for separation of solutes according to their partition coefficients. Application of this technique has been successfully demonstrated by separation of analytes by gas–liquid and liquid–liquid two-phase systems. However, the method cannot be directly applied to the system with a set of coiled columns connected in series, since the countercurrent process is interrupted at the junction between the columns. However, this problem can be solved by intermittent dual CCC by eluting each phase alternately through the opposite ends of the separation column. This mode of application has an advantage over the conventional dual CCC in that the method can be applied to all types of CCC systems including hydrostatic equilibrium systems such as toroidal coil CCC and centrifugal partition chromatography. Recently, the application of this method to high-speed CCC (hydrodynamic system) has been demonstrated for separation of natural products by Hewitson et al. using a set of conventional multilayer coil separation columns connected in series. Here, we have developed a mathematical model for this intermittent dual CCC system to predict retention time of the analytes, and using a simplified model system the validity of the model is justified by a series of basic studies on both hydrodynamic and hydrostatic CCC systems with a computer-programmed single sliding valve. The present method has been successfully applied to spiral tube assembly high-speed CCC (hydrodynamic system) and toroidal coil CCC (hydrostatic system) for separation of DNP-amino acid samples with two biphasic solvent systems composed of hexane–ethyl acetate–methanol–0.1 M hydrochloric acid (1:1:1:1 and 4:5:4:5, v/v).

Rapid determination of carbamate pesticides in food using dual counter-current chromatography directly interfaced with mass spectrometry

Dual counter-current chromatography (dual CCC)–tandem mass spectrometry (MS/MS) was successfully performed with a newly designed spiral column for dual CCC. The small column capacity required for directly coupling with electrospray MS/MS was accomplished by forming a rectangular spiral groove on a plastic disk and sealing it with a PTFE sheet. This novel dual CCC–MS/MS technique was successfully applied for the rapid determination of methomyl, fenobucarb and carbaryl pesticides in food. A two-phase solvent system of n-hexane-acetonitrile-0.1% formic acid (45:45:10) was suitable for both good dual CCC separation and sufficient ionization of pesticides. Recoveries of these three pesticides from mandarin orange and spinach samples fortified at 0.05 mg/kg were in the range of 93–107% with relative standard deviations of 2.4–3.8%.

Modelling counter-current and dual counter-current chromatography using longitudinal mixing cell and eluting counter-current distribution models

Two well known approaches are considered to analyze the processes of counter-current and dual counter-current chromatography: the longitudinal mixing cell model and the Craig's counter-current distribution model. The cell model represents perfectly mixed, equally sized cells in series. The number of cells characterizes the rates of longitudinal mixing in the stationary and mobile phases. In the eluting counter-current distribution (CCD) model, the CCC process is considered as a continuous form of Craig's counter-current distribution. For a cascade of equilibrium stages theoretical elution profiles of the CCC process by using the CCD and cell model approaches have been compared. It is shown that in general, distribution functions of the CCD and cell models differ. It is established that the distribution of a solute between two solvent phases in the dual CCC process is determined by the extraction factor c, the total number of equilibrium stages n and the position of the sample inlet m by the equation Q x = (1 − c m)/(1 − c n + 1 ) with c = F 2 K D/ F 1 ( K D, F 1, F 2 and Q x are the distribution constant, the phase flow-rates and the portion of solute eluted by the first phase, respectively).

Analysis of new counter-current chromatography operating modes

Some novel cyclic operating modes of counter-current chromatography have been suggested. Chromatographic separation processes with two zones of different partition coefficients and with extraction and scrubbing (washing) zones are mathematically described using the eluting counter-current distribution approach. Two possible cyclic modes of dual counter-current chromatography operation, with simultaneous and alternate transfers of the phases, are analyzed. It is shown that the operating mode with the alternate transfers of the phases provides considerably higher separation efficiency than the mode with simultaneous transfers of both phases.

High Throughput Analysis of N‐Methyl Carbamate Pesticides in Cereals and Beans by Dual Countercurrent Chromatography and Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometry

We developed a new analytical method for analysis of N‐methyl carbamate pesticides in cereals and beans using dual counter‐current chromatography (dual CCC) and liquid chromatography‐electrospray ionization tandem mass spectrometry (ESI LC/MS/MS). After pesticides were extracted from cereals and beans with ethyl acetate, each extract was cleaned up by dual CCC using a non‐aqueous binary solvent system composed of n‐hexane‐acetonitrile and analyzed by ESI LC/MS/MS with a short column. The average recoveries from cereals and beans fortified at the level of 0.01 ppm ranged from 73.9 to 119.6%, with the coefficients of variation from 0.7 to 6.8%. At the fortified level of 0.5 ppm, the recoveries ranged from 72.1 to 117.1% with coefficients of variation from 0.4 to 9.3%. The present analytical method of N‐methyl carbamate pesticides in cereals and beans is considered to be useful for monitoring the pesticide residues in cereals and beans.

Application of dual counter-current chromatography for rapid sample preparation of N-methylcarbamate pesticides in vegetable oil and citrus fruit

Dual counter-current chromatography (dual CCC) has been successfully applied to rapid sample preparation for the simultaneous determination of residual carbaryl, fenobucarb and methomyl in vegetable oil and citrus fruit. The citrus fruit samples were extracted with n-hexane solution containing stable isotopically labeled internal standards (methomyl-d3, fenobucarb-d3 and carbaryl-d9), and applied to dual CCC using a two-phase solvent system of n-hexane–acetonitrile to purify the carbamate pesticides from aliphatic sample matrix. The coiled column was rotated at 420 rpm, the lower mobile phase was introduced through the head toward the tail, and the upper mobile phase in the opposite direction. Due to the high partition efficiency of dual CCC, the lower phase fraction collected from 2 to 5 min after injection could be subjected to flow-injection tandem mass spectrometry directly after concentration. Repetitive sample injection can be performed at high reproducibility without a risk of contamination from the compounds retained in the column.

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...

Trends in countercurrent chromatography

Since the early 1970s countercurrent chromatography has achieved a remarkable advance and is currently yielding rapid and efficient chromatographic separations that are comparable with those obtained with preparative high-performance liquid chromatography. The method further provides unique applications such as partition with polymer phase systems, foam separation and liquid—liquid dual countercurrent chromatography.