This thesis presents work on electrohydrodynamic focusing (EHDF) and photon transmission to aid the development of species preconcentration and identification. EHDF is an equilibrium focusing method, where a target ion becomes stationary under the influence of a hydrodynamic force opposed by an electromigration force. To achieve this one force must have a non-zero gradient. In this research a novel approach of using a 2-dimensional planar microfluidic device is presented with an open 2D-plane space instead of conventional microchannel system. Such devices can allow pre-concentration of large volume of species and are relatively simple to fabricate. Fluid flow in these systems is often very complex making computer modelling a very useful tool. In this research, results of newly developed simulations using COMSOL Multiphysics® 3.5a are presented. Results from these models were compared to experimental results to validate the determined flow geometries and regions of increased concentration. The developed numerical microfluidic models were compared with previously published experiments and presented high correspondence of the results. Based on these simulations a novel chip shapes were investigated to provide optimal conditions for EHDF. The experimental results using fabricated chip exceeded performance of the model. A novel mode, named lateral EHDF, when test substance was focused perpendicularly to the applied voltage was observed in the fabricated microfluidic chip. As detection and visualisation is a critical aspect of such species preconcentration and identification systems. Numerical models and experimental validation of light propagation and light intensity distribution in 2D microfluidic systems was examined. The developed numerical mode of light propagation was used to calculate the actual light path through the system and the light intensity distribution. The model was successfully verified experimentally in both aspects, giving results that are interesting for the optimisation of photopolymerisation as well as for the optical detection systems employing capillaries.