Application of coil centrifugal counter-current chromatography to the separation of macrolide antibiotic analogues III. Effects of flow-rate, mass load and rotation speed on the peak resolution

As the third part of our methodology studies on the application of centrifu gal counter-current chromatography to the preparative separation of macroli de antibiotic analogues, we have investigated the effects of various parame ters on the retention of stationary phase and peak resolution. Our results show that the retention percentage of the stationary phase has linear relat ionships with both flow-rate at 1 to 3 ml/min and rotation speed at 100 to 700 rpm, but their correlation coefficients are negative (-1.000) and posit ive (0.9821), respectively. The peak resolution (R-s) is inversely proporti onal to the flow-rate (F-r) and mass load (M-1), but directly proportional to the rotation speed (R-rev). Their correlation coefficients in linear reg ression for the preparative separation in laboratory scale are -0.981 to -1 .000 for R-s = a + bF(r) at flow-rates of I to 3 ml/min, -0.929 to -0.993 f or R-s= a + bM(1) at mass loads of 12.5 to 100 mg, and 0.975 to 0.998 for R -s = a + bR(rev) at rotation speeds of 300 to 700 rpm, respectively. Prepar ative separation of six very closely related macrolide antibiotics, which b elong to ascomycin and rapamycin analogues, has also been successfully achi eved under optimized conditions. (C) 2001 Elsevier Science B.V. All rights reserved.