One of the main issues associated to the development of photocatalysis is the lack of adequate indexes that allow the comparison of the results obtained in different experimental setup designs. The hydroxyl radicals ((OH)-O-center dot) generation rate is a key factor to determine the overall oxidation rate. In this work, using a Light Emitting Diodes (LEDs) reactor aimed to maximize light efficiency and minimize energy consumption, the (OH)-O-center dot generated have been determined as a function of the radiation and catalyst concentration following an indirect method based on the reaction between (OH)-O-center dot and dimethyl sulfoxide (DMSO) to produce formaldehyde. Finally, the methodology has been applied to analyze the degradation kinetics of the anionic surfactant dodecylbenzenesulfonate (DBS), frequently used in shampoo formulations and detergents for washing machines. We propose a method based on the indirect determination of (OH)-O-center dot radicals generation rate that allows the assessment and comparison of the kinetics of photocatalytic oxidation of pollutants. (C) 2014 Elsevier B.V. All rights reserved.