Direct photo-production of singlet oxygen, via 1270 nm laser excitation of molecular oxygen, has been the focus of recent articles. The chemical traps 1,3-diphenylisobenzofuran and rubrene are used to monitor singlet oxygen production in organic solvents through the O-2 [(3)Sigma(-)(g)] -> O-2 [(1)Delta(g)] transition. In this Letter evolution of the trap concentration is monitored continuously and we propose a new and simple method to measure singlet oxygen production rate. We derive an analytical expression for the trap disappearance rate that allows simultaneous and independent determination of the 1270 nm absorption cross section and the half quenching concentration with the chemical trap. (C) 2012 Elsevier B. V. All rights reserved.