Advantages of rectangular horizontal tubing in the semi-preparative counter-current chromatography bobbin

Counter-current chromatography (CCC) is a widely used liquid-liquid separation technique. Much work has been performed to improve the retention of stationary phases and throughput. In previous research, high aspect ratio rectangular horizontal (RH) tubing has been proven to be able to improve resolution and throughput in comparison with standard circular (SC) tubing. However, those modifications and improvements of tubing shapes have only been tested on analytical tubing thus far. This study aims to verify whether RH tubing could achieve similar high stationary phase retention (Sf) and throughput on a semi-preparative CCC apparatus. First, a lighter and larger volume semi-preparative bobbin with thin-wall RH tubing was successfully manufactured. Then the Sf of this bobbin was tested with n-hexane-ethyl acetate-methanol-water (HEMWat) and dichloromethane-methanol-water (DMW) solvent systems, and its maximum throughput was explored with the mixture of Magnolia officinalis Rehd. Et Wils. The results show that the thin-wall RH tubing bobbin can retain high Sf for these solvent systems, even at a relatively high mobile phase flow rate, which is consistent with the analytical bobbin results. The throughput test demonstrates that 2.12 × throughput can be obtained with the RH tubing column bobbin compared to the conventional SC tubing column bobbin without changing the outside dimensions of the bobbin. The present study is a necessary step for the application of the RH tubing bobbin from a laboratory analytical scale to preparative industrial scale.