IMPORTANCE OF THE PARAMETER VM/VC IN COUNTERCURRENT CHROMATOGRAPHY - TENTATIVE COMPARISON BETWEEN INSTRUMENT DESIGNS

Results acquired with three CCC devices are compared. There is a linear relationship between the minimum volume of mobile phase, V(m)min, compatible with the actual flow rate, F, and that flow rate. Vc being the volume of the column and S the cross sectional area of the channel where the chromatographic process occurs, the slope of the line V(m)min/Vc = f (F/S) allows comparison of the stability of the stationary phase for various instruments. This relationship leads to an estimation of the average linear velocity of the mobile phase in the channel, uBAR, namely V(m)min/V(c) = (1-d)/uBAR F/S + d, d being the relative volume in the ducts and flow tubes in the column. The efficiency is much more dependent on the relative volume of the mobile phase than it is on the flow rate for the three instruments, and it generally increases with the relative volume of the mobile phose in the column. As a result, the resolution decreases very slowly, or not at all, when F and V(m)min are increased.