The activity hereby presented is part of a project aimed at developing a compact all-fibre setup that exploits the Surface Plasmon Resonance (SPR) phenomenon to detect changes of chemical composition in a flowing liquid. The work has reached a lab prototype level, consisting of a plastic pipe with an embedded multi-mode optical fibre SPR sensor used as a refractometer. A demonstrator has been realised connecting the pipe to a water reservoir through a recirculating pump. Introduction of a contaminant into the flowing water produces a shift of the SPR. The system, tested with isopropyl/water mixtures, shows the capability to measure refractive index variations with a sensitivity of 2000 nm/RIU (RIU stands for Refractive Index Unit). The control unit is developed upon a commercial easy-to-use platform for demonstration and educational purposes.