Edinburgh Instruments is pleased to announce the stopped flow accessory for the FLS1000 Fluorescence Spectrometer which enables reaction kinetics to be recorded with microsecond time resolution.

The understanding of reaction kinetics is an important area of study across biology and chemistry. By studying kinetics; the reaction rate, reaction order and the underlying molecular mechanism can be determined. A powerful method for determining the kinetics of a reaction is by monitoring the concentration of the reactants or products over time using absorption or fluorescence spectroscopy. For slow reactions, the reactants can simply be mixed by hand or using a magnetic stirrer. However for fast reactions, where the lifetime of the reaction is comparable with the mixing time, more specialised techniques must be used such as stopped flow.

FLS1000 equipped with stopped flow accessory.

In stopped flow the reactants are loaded into syringes and quickly injected into an observation cuvette where they rapidly mix and the change in absorbance or fluorescence intensity recorded as a function of time. Edinburgh Instruments offers a stopped flow accessory for both the FLS1000 and the FS5 Fluorescence Spectrometers as well as the LP980 Transient Absorption Spectrometer, extending the capability of these systems for the measurement of rapid reaction kinetics. A high temporal resolution is crucial for the measurement of rapid reaction kinetics. Stopped flow kinetic scans can be measured with 10 ms temporal resolution on the FS5 and < 0.1 ms on the FLS1000, which enables reactions with rate constants as fast as 100 s^-1 to be easily measured on the FLS1000 using the stopped flow accessory.

Kinetic trace of the fluorescence quenching of N-acetyltryptophanamide with N-bromosuccinimide. Monoexponential fitting reveals a reaction rate constant of 35 s-1. Data was acquired using MCS mode on the FLS1000. Addition of 5 consecutive scans.