Mixing time correction, stopped-flow

The limit for the measured rate constants is determined by the mixing rate and the instrument s dead time, defined as the time required for the solution to travel from the mixing chamber to the observation point. Nowadays, half-times in the millisecond range can be measured routinely. An extension of accessible rates up to 2000 s through algebraic corrections for mixing effects was discussed [11]. Under the assumption that the behavior of the solution at short times after mixing in the stopped-flow is described by the same equations that were found applicable for pulsed-accelerated flow, the precise rate constant can be obtained from a set of experiments carried out under pseudo-first-order conditions by use of Eq. 10. 

The dead time is typically 3-5 ms. so stopped flow is not quite as fast as continuous flow, but it requires less than a milliliter of each solution per run. Methods have been described for measuring the dead time " " these are based upon standard reactions whose kinetic behavior is well known. The error introduced by collecting data before mixing is complete can be corrected." ... 

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