Detection of Hydroxyl Radicals by a Chemiluminescence Method - A Critical Review

A chemiluminescence (CL) method for the sensitive and selective detection of free hydroxyl radicals has been investigated. The CL method is based on hydroxylation of non-chemiluminescent phthalic hydrazide by hydroxyl radicals to give the strongly chemiluminescent 3-hydroxyphthalic hydrazide. The selectivity of the method was tested against some one-electron oxidants, including the highly reactive sulphate anion radical. No hydroxylation of phthalic hydrazide was observed with these oxidants, showing that the method is selective for the hydroxyl radical. The CL method showed a high sensitivity : detection at a level of 0.1 picomole 3-hydroxyphthalic hydrazide was reached. In our studies on the role of the hydroxyl radical in the fungal degradation of wood and in the bleaching of pulp the method has proven to be reliable and has contributed in a crucial way to the results obtained. The method may also be suitable for in vivo studies.