Mathematical Model for the Luminol Chemiluminescence Reaction Catalyzed by Peroxidase
Lin Li,' Mark A. Arnold,'* and Jonathan S. Dordick2 'Department of Chemistry, *Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa 52242 Received August 24, 1992/Accepted December 29, 1992
A kinetic model that accurately describes intensity vs. time reaction profiles for the chemiluminescence reaction between luminol and hydrogen peroxide, as catalyzed by horseradish perioxdase, is derived and evaluated. A set of three differential equations is derived and solved to provide intensity time information for the first 200 seconds of the reaction. The model accurately predicts intensity-time profiles when literature values are used for all but one of the reaction rate constants. Furthermore, the model predicts a nonlinear curve for plots of light intensity versus the initial hydrogen peroxide concentration. Experimental data confirm that such plots are nonlinear. Finally, a linear double-reciprocal plot is predicted by the model and the experimental data verify this relationship. 0 1993 John Wiley & Sons, Inc. Key words: luminol chemiluminescence peroxidase hydrogen peroxide

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INTRODUCTION
Chemiluminescence (CL) is a phenomenon that provides for rapid and sensitive analytical measurements. Light generated by biocatalytic approaches offers high selectivity in combination with reasonable quantum yields at near neutral pH levels. Peroxidases are known to catalyze light generation upon the oxidation of luminol in the presence of hydrogen peroxide. This is particularly useful in coupled reactions with oxidases to measure a wide variety of clinically, biomedically, and chemically important compounds.1 2 5 11,13
7 7 7

state 3-aminophthalate (3-AP) is the light emitting species that forms directly from LO*H-. Because 3-AP can be generated by a number of different, and simultaneous reaction steps, the observed generation of light at a given