The Luminol's reaction can be triggered through a wide range of catalysts, more or less specific for a particular oxidizing species and with varying efficiencies.
The complex mechanism of the peroxidase-catalysed reaction and the stoichiometry remain hypothetical. Roughly speaking, the reaction sequence leading to light generation can be divided into two main processes. First, in the course of a series of enzymatic steps and in the presence of luminol (LH-) and hydrogen peroxide, horseradish peroxidase (HRP) is successively converted into intermediary complexes (complex I and complex II) before being regenerated to free peroxidase. These enzymatic steps produce luminol radicals (L-, LH.) which then enter a complex chemical pathway to finally generate luminol hydroperoxide (LO2H), the precursor of the light emitter (excited 3-aminophthalate ion).
Finally, transition metal cations (Co2+, Cu2+, Cr2+,
Fe2++, Fe3+, Hg2+, Mn4+, Ni2+) and their complexed
forms (e.g. ferrocene, ferricyanide) can be used as catalyst
with mitigated performances which are linked to the relatively
low signal to noise ratio obtained and the required
elevated pH of the reaction.
The electrochemical oxidation of luminol is usually
considered as the second most efficient way of triggering
the reaction. The scheme is similar to the peroxidasecatalysed
one with hydrogen peroxide as co-oxidant and a
large range of working pH.