Quench flow apparatus is used to study fast reactions, enabling the stopping (or quenching) of the reaction. By stopping the reaction at specific time points, the rate can be determined through plotting the concentration of product / reactant against time.
This method is much faster and more precise than traditional methods, allowing for more accurate data to be obtained. As the process is automated, it is possible to study faster reactions than would be possible when doing the same process by hand.
A traditional quenching method may involve the scientist transferring the reaction, at a defined time interval, to a quenching agent. This will cease the reaction, but the scientist will be too slow for many biological reactions.
However, this apparatus is highly specialised, and may be cost-prohibitive.