A microfluidic-based system has been developed for copper (II) monitoring in water samples with sensitive and selective detection, based on the measurement of light emitted from the copper (II) catalysed oxidation of 1,10-phenanthroline by hydrogen peroxide. Work initially focussed on the development of a flow injection analysis (FIA) system with micellar enhanced chemiluminescence (CL) detection. Sufficient selectivity was achieved by removing interfering metal ions using an on-line itaconic acid modified microcolumn, allowing copper (II) to be easily determined at concentrations as low as 1 jig L_1 from high concentrations of calcium (II) and magnesium (II). The FIA-CL system was further developed and scaled-down to create a microfluidicbased system. A number of different microflow devices, of various designs and dimensions, were manufactured from polymethylmethacrylate (PMMA). A range of in-house micro-fabrication techniques were investigated for the fabrication of the microfluidic devices including hot embossing, laser ablation and direct micromilling. A complete miniaturised flow system was developed incorporating miniaturised peristaltic pumps, a microfluidic plastic manifold and a compact photomultiplier tube for CL detection. Experimental conditions including reagent concentrations and flow rates were optimised and the system was found to produce linear results for copper (II) over the concentration range 0 to 150 jxg L‘\. Selectivity of the microfluidic-based CL system was further enhanced by incorporating an on-line separation step into the microflow manifold. A number of different solid phases were compared and contrasted for the on-line separation of copper (II) from complex sample matrices. These included incorporating a stationary phase e.g. monolithic and chelating resin micro-columns into the plastic microflow device and the use of on-line modified Convective-Interaction Media® (CIM®) disk monolithic columns. Finally the optimised system was successfully used for trace copper (II) determinations in a standard reference freshwater sample (SRM 1640) and in real water samples.