Setup and validation of an improved pulsed-accelerated-flow spectrophotometer
Abstract
An improved pulsed-accelerated-flow spectrophotometer measures fast reactions, with half-lives as small as 1.4 $\mu$s by varying the velocity with which reactants are injected into an observation-mixing tube illuminated by visible or uv light. The measurement by integrating observation occurs while the solutions are flowing and the light path includes the point of mixing. Precise control of the flow velocity and accurate determination of small absorbance changes are necessary. The setup and validation of the motion control system and calibration of the absorbance measurements are described. The effect of spurious absorbance changes is predicted and methods for either eliminating or correcting for them are developed. The instrument is calibrated with a known electron transfer reaction up to a pseudo-first-order rate constant of 500,000 s$\sp{-1}$. These reactions are so fast that the mixing that occurs at the point of injection becomes a factor and a modified data analysis model is developed. The instrument and model are applied to the proton transfer reaction of an indicator (chlorophenol red to imidazole).
Degree
Ph.D.
Advisors
Margerum, Purdue University.
Subject Area
Analytical chemistry|Chemistry
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