FLOW-INJECTION SYSTEM FOR DETERMINATION OF SINGLET OXYGEN QUENCHING EFFICIENCIES UTILIZING ONLINE DIOXETANE CHEMILUMINESCENCE DETECTION

Quenchers of singlet oxygen are believed to exhibit a protective actio n against oxidative stress. Previously, the bimolecular quenching rate constants have been determined by means of elaborate batch experiment s. In the present paper a novel analytical technique is presented, i.e . a flow injection system in which photochemically generated singlet o xygen reacts on-line with 1,2-diethoxyethene to form 3,4-diethoxy-1,2- dioxetane. In the detector cell thermal decomposition (70 degrees C) i n the presence of a fluorophore (9,10-dibromoanthracene-2-sulfonate) l eads to chemiluminescence (CL). Upon injection of a quencher a decreas e of the CL intensity is observed and, as outlined theoretically, the associated singlet oxygen quenching rate constant can readily be deter mined. Furthermore it is shown that effects of interferences can easil y be accounted for experimentally. Obtained data are in good agreement with available literature data, provided that solvent influences are considered. The novel method is fast, and quenching rate constants in a wide variety of solvent compositions can readily be obtained.