Reaction Kinetics with Flowthrough Colorimetry

The customary colorimetric initial and integrated rate procedures for determining kinetic reactant orders involve a significant determinate error arising from the system setup time delay before the first absorbance value is recorded after combination of the reactant solutions initiates the reaction. To eliminate this error source, a modified experimental procedure is described in which absorbance measurement is initiated from the moment that the reactant solutions are combined and an interpolation step is introduced to represent the absorbance versus reaction time relationship over the opening period before the first absorbance value of the test solution is recorded. To investigate the effectiveness of this interpolation step in eliminating experimental error, in the present study the colorimetric procedure was repeated in a test system modified to operate in a flowthrough mode to deliver absorbance values from the moment that the reactant solutions are combined.