During reactive liquid-liquid extraction, the mass transfer between phases is commonly considered as controlled either by the kinetics of the chemical reaction at the interface or by the diffusion of the solute through the two boundary layers. A fine knowledge of the mass transfer control step is a key element to develop a full phenomenological model of a new liquid-liquid extraction process. Kinetics studies usually enable only to determine an overall (global) kinetic constant which includes a minima both phenomena. The present paper discusses the various methods allowing the discrimination be-tween diffusion and chemical kinetics when studying the extraction of uranium(VI) from a nitric aque-ous stream by a monoamide solvent. In the case mentioned earlier, the extraction of U(VI) in HNO3 by monoamides, a cross comparison of the results obtained with complementary techniques as single drop, Nitsch cell and rotating mem-brane cell allowed us to estimate the contribution of the chemical mass transfer. To go further, the microfluidics technology was chosen as an interesting way to study such kinetics: it offers a well-controlled interfacial area, a significant decrease of contact times and a reduction of the molecular diffusion length. Then, an original experimental setup using high velocity phases into a microfluid-ics chip has been developed to dramatically reduce the diffusion contribution during mass transfer. Mass transfer studies on monoamide based extraction systems have also been achieved with mi-crosystem apparatus. Determining the overall global mass transfer coefficient from these experi-ments according to the two film theory, the comparison of the results with the single drop technique suggests an increase of the mass transfer regime at the micro scale. Regarding the increase of uranium(VI) transfer kinetics when determined by the microfluidics technol-ogy, we assume that the diffusion phenomenon is minimized and that the implemented experimental setup allows a closer estimation of the chemical transfer contribution.