Recovery and recycling of solvent of counter-current chromatography: The sample of isolation of zeaxanthin in the Lycium barbarum L. fruits.

An efficient method of recovering and recycling solvent for counter-current chromatography was established by which zeaxanthin was separated from Lycium barbarum L. fruits. A column with activated carbon combined with high performance counter-current chromatography formed the recovering and recycling solvent system. Using the solvent system of n-hexane-ethyl acetate-ethanol-water (8:2:7:3, v/v) from the references, five injections were performed with an almost unchanged purity of zeaxanthin (80.9, 81.2, 81.5, 81.3, and 80.2% respectively) in counter-current chromatography separation. Meanwhile, the mobile phase reduced by half than conventional counter-current chromatography. By this present method, an effective improvement of counter-current chromatography solvent utilization was achieved.

Counter-current chromatography melamine-modified column and its separation mechanism.

In this work, to further verify and develop the novel counter-current chromatography modified column separate mode, a melamine modified counter-current chromatography column was prepared. Meanwhile, the modified counter-current chromatography column was used to separate stevioside and rebaudioside A with the same partition coefficient in chosen solvent system to evaluate its separation efficiency. The results show that because of the presence of intermolecular forces between melamine and model compounds, better separation could be achieved on the modified column while it's almost impossible to be separated on the unmodified column. So the results of this research further show that column modified method is a possible approach to further increase the separation ability of counter-current chromatography. Take advantage of large sample handing capacity of counter-current chromatography, the mothed may have great potential to be an efficient method of separation and preparation enantiomer compounds.

Isolation of high-purity peptide Val-Val-Tyr-Pro from Globin Peptide using MCI gel column combined with high-speed counter-current chromatography.

Peptides have gained increased interest over the past several decades because of their therapeutics. In this research, a strategy combining MCI gel column chromatography and high-speed countercurrent chromatography was developed for the separation of high-purity peptide Val-Val-Tyr-Pro from Globin Peptide. First, the fraction of Val-Val-Tyr-Pro mixtures with a purity of 15.8% was obtained by using MCI gel column with a mixture of ethanol/water (20:80, v/v/v). Then, the high-purity Val-Val-Tyr-Pro was separated by high-speed countercurrent chromatography with a aqueous two phase systems of ethanol/acetonitrile/iso-propyl alcohol/(NH4 )2 SO4 Saturated solution /H2 O (0.5:0.5:0.25:1.5:0.7,v/v). The ammonium sulfate from high-speed countercurrent chromatography fractions was removed from target compound by MCI gel column chromatography using ethanol/water in stepwise elution mode. A 78 mg of Val-Val-Tyr-Pro was successfully purified with the purities of 98.80% from 30 g crude Globin Peptide. The amino acid sequence of the Val-Val-Tyr-Pro was determined by electrospray ionization high resolution tandem mass spectrometry. The method presents a practical strategy for the large-scale separation of pure peptide Val-Val-Tyr-Pro from Globin Peptide, and provides a reference method for obtaining high-purity peptide from other polypeptide mixtures.

A simple gradient equilibrium method for better separation in countercurrent chromatography.

The stationary phase retention is one of the most important parameters in countercurrent chromatography. In this work, a simple gradient equilibrium method was developed to further improve the stationary phase retention based on the optimized condition in the traditional equilibrium model. Meanwhile, this novel gradient equilibrium method was used to separate three flavone model compounds and compared with the conventional isocratic equilibrium method to evaluate the separation efficiency. The results show that better resolution or shorter separation time could be achieved with gradient equilibrium compared to isocratic equilibrium. So this novel equilibrium method has enormous potential for obtaining a better separation or saving the separating time in the preparative separation of target compounds.

The development of biphasic chiral recognition in chiral separation.

In chiral separation, enantioseparation factor is an important parameter which influences the resolution of enantiomers. In this current overview, a biphasic chiral recognition method is introduced to the readers. This method can significantly improve the enantioseparation factor in two-phase solvent through adding lipophilic and hydrophilic chiral selectors which have opposite chiral recognition ability to organic and aqueous phases, respectively. This overview presents the development and applications of biphasic chiral recognition in liquid-liquid extraction and counter current chromatography. It mainly focuses on the topics of mechanism, advantages and limitations, applications, and key factors of biphasic chiral recognition. In addition, the future outlook on development of biphasic chiral recognition also has been discussed in this overview.

Surface modification of polytetrafluoroethylene column for two-stationary phase separations by counter-current chromatography.

To improve the separation capability of CCC, a novel solid-liquid two-stationary phases CCC (ASP-CCC) column was prepared employing graphene oxide (GO) conjugated poly-dopamine (PD) coating (GO/PD) as auxiliary stationary phase (ASP). The results of Scanning electron microscopy (SEM), contact angle and X-ray photoelectron spectroscopy (XPS) indicated that nanostructured GO and PD were successfully grafted on the inner wall of the PTFE column. Three alkaloid compounds were selected as the target analytes to evaluate the performance of the novel column. Because of the intermolecular force (hydrogen bond, electrostatic interaction and π-π interaction) between the ASP and model compounds, three analytes were well separated with this novel ASP-CCC column. Additionally, the novel column exhibited higher stationary phase retention ratio, about 8%, than original column without changing the chromatographic condition. Furthermore, the eluotropic sequence of analytes on novel column was in accordance with that in the original column. This suggested that the novel column is a CCC column with auxiliary stationary phase (ASP) in its own right, and the present separation mode is the combination of partition chromatography and adsorption chromatography.