We present an electrochemical sensor system for the detection of hydrogen peroxide inside a direct synthesis microreactor. The setup allows the online, in situ measurement of high reactant concentrations by amperometric detection across the micro channel width and length. The robust integration of the electrochemical cell in the microreactor was demonstrated. Hydrogen peroxide was detected under reaction conditions (pH 3–4, presence of bromide) showing linear behaviour up to 2 mM with high sensitivity and excellent stability. The linear range was increased up to 10 mM by applying a diffusion limiting pHEMA layer to the electrode surface.
