Small molecules, such as ferrocenemethanol (FcMeOH) and O-2, that are capable of quenching the Ru(bpy)(3)(2+) excited state via energy or electron transfer can be quantitatively detected in a bipolar electrochemical cell based on the attenuation of steady-state electrogenerated chemiluminescence (ECL). FcMeOH quenches ECL generated by the Ru(bpy)(3)(2+) oxalate coreactant system, exhibiting a linear dependence on [FcMeOH] with a Stern-Volmer slope of 921 M-1, corresponding to a quenching rate constant of 2 x 10(9) M-1 s(-1). We used the bipolar ECL quenching platform to measure dissolved O-2 and validated the results using a standard Clark electrode. The detection limit for local [O-2] measured using ECL quenching was found to be 300 ppb. This work opens up the possibility of utilizing ECL quenching at bipolar electrodes for a wide range of applications.