Studies on the performance of different coiled column configurations for compact type‐I countercurrent chromatography

Abstract

Three types of novel coiled column configurations, i.e., a triangular coiled column and elliptical coiled columns I and II, were designed for type-I countercurrent chromatography and their performances were evaluated with two solvent systems each with suitable test samples. Three DNP-amino acids (DNP-DL-glu, DNP-β-ala and DNP-L-ala) were separated with a moderately hydrophobic two-phase solvent system composed of hexane-ethyl acetate-metanol-0.1M hydrochloric acid (1:1:1:1, v/v), while two dipeptides (tryptophyl tyrosine and valyl-tyrosine) were separated with a polar solvent system composed of 1-butanol-acetic acid-water (4.75:0.25:5, v/v). The overall results indicated that the performance of compact type-I counter-current chromatography was improved by elliptical coiled column II which was mounted with its maximum coil diameter perpendicular to the surface of the column holder. Hydrodynamic effects involved in these separations were discussed.

Evaluation of the performance of protein separation in figure-8 centrifugal counter-current chromatography

“…When the column was parallel to the acting centrifugal force field, the best Rs was obtained in both DNP-amino acid and dipeptide separations, each done with a suitable two-phase solvent system. We speculated that the double loop of the figure-8 column provides two separate segments each producing droplet flow of mobile phase to increase the interface area for mass transfer and improve the peak resolution (Rs) [18]. In this study, the protein samples were separated by this figure-8 centrifugal hydrostatic CCC system.…”

“…The lower flow rate can provide enough time to produce a prolonged droplet flow of the mobile phase, which provides a large interface area to enhance the mass transfer process. This may explain high performance obtained by a lower flow rate of the mobile phase in the figure-8 column [18]. …”

“…A total of 18 column units are serially connected with transfer tubing to form a figure-8 separation column with a total capacity of 3.4 ml. Each figure-8 column is mounted around the periphery of the rotary platform arranged equally spaced with the acting centrifugal force field [18]. Each terminal of the column is connected to a PTFE flow tube (0.46 mm I.D., Zues Industrial Products) with a set of tubing connectors (Upchurch Scientific, Palm Spring, CA, USA).…”

“…Based on these findings, the performance of the figure-8 column was investigated in a centrifugal hydrostatic CCC for the separation of dipeptide mixtures and DNP-amino acid mixtures by changing the angle between the column axis and centrifugal force. The results indicated that the highest Rs was obtained when the figure-8 column was parallel to the radially acting centrifugal force field, [18]. …”

Countercurrent Separation of Natural Products: An Update

“…The best configurations were obtained by connecting a left-handed column with a right-handed column tail-to-head or by connecting a left-handed column with another left-handed column tail-to-head. 54 − 57 …”