Gas-phase chemical sensing using electrochemiluminescence

Tris (2,2'-bipyridine) ruthenium (III) (Ru(bpy)(3)(3+)), an electrogenerable, chemiluminescent reagent which is electrochemically reversible, has been demonstrated to be a suitable reagent for the sensitive detection of gas-phase hydrazine, and its derivatives dimethyl hydrazine and monomethyl hydrazine. The electrochemical oxidation of Ru(bpy)(3)(2+) to Ru(bpy)(3)(3+) creates a strong oxidizer, whose reduction back down to Ru(bpy)(3)(2+) by reaction with a reducing analyte is typified by the emission of a photon of light centered at 610 nm. A portable and semiportable instrument which rely upon the chemiluminescent reactivity and reversibility of the Ru(bpy)(3)(3+) reagent have been designed and tested. Detection limits for hydrazine and its derivatives have been obtained in the low ppb regime, while response times are on the order of seconds to several minutes, depending upon the analyte being examined. The sensitivities of these devices are strongly pH-dependent due to the effect pH has on both the lifetime of the Ru(bpy)(3)(3+) reagent, as well as on the reactivity of the hydrazine derivatives.