Rapid quench-flow is a well-established kinetic technique where the experimentalist can isolate intermediates and products within a reaction mechanism and analyse them by analytical methods providing a means of specifically identifying these components. This is a complementary technique to stopped-flow and can be used when the reaction does not contain spectroscopic changes or changes cannot identify specific reaction components.

Small volumes of solutions are driven through a high efficiency mixer and flow into a delay (or ageing) loop. After a set time, the reaction is stopped (or quenched) by the addition of a chemical quench solution and flow out of the instrument into a collection tube. The KinTek RQF-3 Quench-Flow Instrument uses a computer-controlled servo motor drive, which provides a precise and reproducible setting of reaction times. Different reaction times in a range of 3-100 milliseconds can be reached by using delay lines with different lengths. By collecting a series of quenched samples, quenched at different times, the kinetics of the reaction can be determined using than appropriate analytical technique.