A fixed-time batch approach for molybdenum determination using iodide oxidation by hydrogen peroxide is presented. The iodine formed was extracted in situ with chloroform, and the absorbance readings were performed at 510 nm. This extraction procedure allowed us to 'freeze' the reaction at any preset time up to two hours, permitting a detailed investigation of the principal and interaction effects among the variables Mo(VI), H2SO4, H2O2, and KI, for the noncatalyzed and the Mo-catalyzed reactions. Response surface methodology was employed to model this chemical system and to find its optimized conditions, resulting in a 12-fold increase in method sensitivity. A reference material (Mussel) from the National Institute for Environmental Studies (NIES, Japan), run under the proposed conditions, gave results in good agreement with the reference value reported for molybdenum.405947959