A simple approach to predict device-specific peak widths in countercurrent chromatography

This study presents a straightforward method for predicting device-specific peak widths in countercurrent chromatography (CCC) with the probabilistic model for immiscible phase separations and extractions (ProMISE). CCC is a liquid-liquid-based separation technique that separates analytes in a (semi-) preparative scale according to the partition coefficient (K value) in both liquid phases. Based on the ProMISE model, peak widths can be calculated mathematically as a function of the efficiency factor f'. Here, we determined factor f' experimentally by examining a CCC run with four alkylresorcinols. Starting with a value of 0.2 in the software ProMISE2, the factor f' was systematically decreased in ProMISE2 until the simulated peak widths fully aligned with those observed experimentally. This resulted in a factor f' = 0.026 for all peaks. Further CCC separations with different substance classes and solvent systems verified that the factor f' = 0.026 was specific for the used QuikPrep MK8 device. Furthermore, the concept was extended to previously published data on a CCC-1000 device, revealing a factor f' = 0.12 for separations of alkyl hydroxybenzoates across six solvent systems. A stable solvent system (no loss of stationary phase during the run) is the prerequisite for the presented method of determining the device-specific factor f'. If this should not be the case with standard applications, other users may apply the solvent system n-hexane/ethyl acetate/methanol/water (9:1:9:1, v/v/v/v) and suitable analytes (similar to alkylresorcinols in this study) for determining the factor f' on their CCC instruments.