A support-free liquid–liquid partition process constitutes countercurrent chromatography (CCC) as practiced in analytical chemistry for the resolution of natural-product and related mixtures. Two immiscible liquid phases are employed: one is retained as the stationary phase by a centrifugal or other hydrodynamic field, while the other is pumped as the mobile phase, so that solutes distribute according to their partition coefficients rather than by adsorption on a solid matrix ^[1]. Because the stationary phase is itself a bulk liquid, the hydrophobicity window of a given solvent system can be extended by elution-extrusion and related operations that recover the liquid stationary phase after the conventional elution window has been exhausted ^[2]. Distinct operating modes, including pH-zone-refining CCC, further organize ionizable solutes into sharp rectangular zones whose boundaries are fixed by acid–base equilibria in the two phases ^[3]. Conceptual boundaries therefore exclude solid-supported liquid chromatography and true countercurrent extraction without chromatographic band development. Essential features are a measurable stationary-phase retention, a defined solvent system (for example Arizona-type alkane/ethyl acetate/methanol/water combinations), and a partition mechanism that does not rely on a solid adsorbent ^[4].