Selective separation of physically near-identical microparticle mixtures by interfacial partitioning

Interfacial partitioning is a novel technology for the separation of physic ally near-identical particles, which are particles with similar densities a nd similar sizes but different chemical compositions. Different crystals pa rtition differently to the interface of a biphasic system, forming a substa ntial interfacial layer (the interphase) as well as a sediment. Here, the s elective separation of ampicillin and phenylglycine crystal mixtures in liq uid biphasic systems is studied as a model system. In a characteristic batc hwise experiment in one step under specific but nonoptimized conditions in water/alkanol biphasic systems, most phenylglycine crystals (80-90% of the feed) adsorb at the interface, whereas the majority of ampicillin crystals (80-90% of the feed) sediment. Important process parameters such as the int erfacial loading, the feed crystal composition, and the volume ratio of the liquid phases have been identified, and their influence on the partitionin g has been studied. We also discuss a possible mechanism of the interfacial partitioning of the crystals on the basis of the formation of an emulsion in the interphase. This technology has tremendous potential for its applica tion in the selective separation of small bioparticle mixtures.