Quantitative determination of singlet oxygen by laser deflection calorimetry

A sensitive method for the quantitative determination of singlet oxygen bas ed on a low-cost laser deflection calorimeter (LDC) apparatus is presented. The heat released from the singlet oxygen generation and its nonradiative decay in an aqueous phase causes the formation of a thermally driven refrac tive index gradient in an adjacent organic phase. This effect, which is pro portional to the amount of singlet oxygen generated, is monitored by the de flection of a laser beam. Limits of detection (LOD) obtained were in the su b-mu mol level which is one order of magnitude lower than the LOD obtained by measuring the "dimol" emission at 633 nm. This method should be speciall y designed for studying chemical and biochemical processes at interfaces by measuring low amounts of heat released.