Stopped-flow

Stopped-flow is one of a number of methods of studying the kinetics of reactions in solution. It is ideal for studying chemical reactions with a typical dead time on the order of 1 millisecond. In the simplest form of the technique, the solutions of two reactants are rapidly mixed by being forced through a mixing chamber, on emerging from which the mixed fluid passes through an optical observation cell. At some point in time, the flow is suddenly stopped, and the reaction is monitored using a suitable spectroscopic probe, such as absorbance, fluorescence or fluorescence polarization. The change in spectroscopic signal as a function of time is recorded, and the rate constants that define the reaction kinetics can then be obtained by fitting the data using a suitable model.

Stopped-flow as an experimental technique was introduced by Britton Chance and extended by Quentin Gibson. Other techniques, such as the temperature-jump method, are available for much faster processes.