Versatile Coil Planet Centrifuge for Performing Countercurrent Chromatography: Comparative Studies on Performance on Three Types of Columns

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Abstract
A compact table top model of a coil planet centrifuge has a capability of utilizing various types of separation columns to yield analytical to preparative separations at high partition efficiency of the helical column on the holder. Three types of helical separation columns were examined to evaluate their performance in retention of the stationary phase and partition efficiency using the same set of peptide samples and butanol two-phase solvent systems. The eccentric helical column consisted of eight coil units each prepared by winding two layers of a 1.6 mm i.d. PTFE (polytetrafluoroethylene) tubing onto a 1.25 cm diameter pipe to yield a total volume capacity of about 12 ml. These column units were interconnected in series with narrow-bore PTFE tubing and symmetrically mounted around the holder at a distance approximately 4 cm from the holder axis. The toroidal column was prepared by winding similar tubing onto a 1.25 cm diameter (plastic flexible) core which was again coiled around the holder. The multilayer column was prepared by winding similar tubing directly around the holder making multiple layers with a total capacity of approximately 240 ml. Overall results indicated that the eccentric helical column yielded higher peak resolution than the toroidal column while the multilayer coil produced the highest peak resolution among all columns. The problem of insufficient retention of viscous sec-butanol/aqueous phase systems in the multilayer column was solved by heating the centrifuge unit at 45–50°C. The toroidal column yielded the lowest efficiency but is most suited for small-scale separations with a narrow-bore coil.