Use of an improved chemiluminescence assay for non-intrusive measurement of hydroxyl radicals in a biomimetic pulp bleaching model system

A chemiluminescence assay was used to measure the production of hydroxyl ra dicals (. OH) in aqueous solutions of hydrogen peroxide and iron-containing catalysts. Preliminary experiments evaluating assay sensitivity revealed t hat one of the required reagents, phthalhydrazide (PtH), interfered with th e studied reactions. In addition, undesirable degradation of the chemilumin escent form of PtH was observed. By removing PtH from reaction solutions an d modifying the published procedures, a successful non-intrusive method for measurement of . OH was obtained. The modified assay was used to compare t he rate of . OH generation in solutions of H2O2, either FeSO4 or Fe-EDTA an d a substrate, lignosulfonate. This "biomimetic" pulp bleaching system is m eant to simulate naturally occurring biological reactions utilized for degr adation of lignins by wood-degrading fungi. Results from these experiments show that FeSO4 produced more . OH than Fe-EDTA. The improved non-intrusive chemiluminescence assay has proven to be an excellent tool for investigati ng the role of the . OH in biomimetic pulp bleaching and potentially other systems.