Ruthenium(II) tris(bipyridyl) ion as a luminescent probe for oxygen uptake

The present work describes an alternative technique for following the rate of oxygen uptake by chemical and enzymatic systems. This method is based on spectrofluorometric monitoring of the well-known quenching effect of molecular oxygen on the emission of the photoexcited [Ru(bpy) 3] 2+ ion, added to the reaction mixtures. The rate of oxygen consumption determined using the present method agrees with that obtained by conventional polarographic techniques in all of the following systems: ascorbate/Cu 2+, glucose/glucose oxidase (EC 1.1.3.4.), and propanal/horseradish peroxidase (EC 1.11.1.7); in the last case, agreement was observed both in the presence and absence of serum albumin and of chloroplasts. Spectrofluorometric data for amphotericin autoxidation in dimethyl sulfoxide are in accord with the rate of decay of the ESR signal of a spin trap added to the reaction mixture. The advantages and limitations of the present spectrofluorometric technique relative to conventional polarographic monitoring of dissolved oxygen are discussed.