Accurate measurements of gas-liquid reactions are difficult and often impossible to obtain owing to the effects of mass transfer, mixing, and a high risk of explosion in cases when oxygen is involved. In this work, a novel reactor concept is introduced that allows the accurate determination of gas-liquid reaction kinetics in a homogeneous liquid phase without the influence of mass transport or mixing effects. Both effects can be bypassed, and the risk of explosion minimized, through the instant dissolution of gaseous oxygen by using a strongly elevated pressure. This work presents an experimental proof of concept of this system with the example of the oxidation of toluene.