Evaluation of the catalytic decomposition of H2O2 through use of organo-metallic complexes--a potential link to the luminol presumptive blood test

Abstract

Forensic scientists use several presumptive tests to detect latent blood stains at crime scenes; one of the most recognizable being the luminol reagent. Luminol, under basic conditions, reacts with an oxidizing species which, with the help of a transition metal catalyst facilitates a luminescent response. The typical oxidizing species used in the luminol reaction is hydrogen peroxide (H(2)O(2)). While the luminol reaction has been studied since its inception, the mechanistic pathway is still an area of great debate. Previous work suggests that the luminol reaction with latent blood stains possesses a correlation to the Fenton-Decomposition reaction mechanism, which decomposes H(2)O(2) into the strongly oxidizing hydroxyl radical (*OH) species. This work seeks to understand the luminol reaction on a mechanistic level and to determine if a synergy exists between the chemiluminescence observed in the reaction and the production of the hydroxyl radical via Fenton-like processes. Results indicate that organo-metallic complexes produce hydroxyl radicals at different rates and different concentrations. These findings appear to be related to structural differences in the organo-metallic complex, which conform to the 18 electron rule or are one electron rich/deficient. Furthermore, the production of *OH is controlled by the chemical environment which governs complex stability at high pH conditions, reflective of the luminol process. Model hemoglobin systems reveal a strong correlation between the rate of *OH production via the Fenton-like pathway and maximum chemiluminescent intensity.