Degussa P-25 TiO2 powder was used as a catalyst in the photocatalytic oxidation of organics. With the objective of promoting a more effective electron-hole separation upon irradiation, the catalyst was modified with small amounts of platinum. Characterisation of the powders was done by X-Ray diffraction and SEM. Chloroform was used as a model molecule and its degradation followed using selective electrodes, with excellent results for the modified titania. Langmuir-Hinselwood kinetic was used to describe the heterogeneous oxidation of chloroform on TiO2, for low solute concentrations.