For merging two facets of process intensification, namely, slug flow in microcapillaries and ionic liquid extraction, the fluid mechanic stability of organic-ionic liquid slug flow is mapped for [EMIM] [Alkyl-SO4] and [Alkyl-MIM] [Ntf2] in 0.5-1.0mm ID plastic capillaries. The choice of the ionic liquid solvent is restricted by physical properties. The internal circulation within ionic liquid slugs is found to be slower by a factor of 2-10 compared to aqueous slugs, but is accelerated by optimizing velocity, temperature, and wall material. Extraction of acetic acid from n-heptane with EMIM ethyl sulfate is proposed as a system to verify the contribution of internal circulation to mass transfer. In the long run, this research affirms the fluid dynamic feasibility of microcapillary slug-flow extraction with ionic liquids.