Singlet oxygen (1O2) is a photochemically produced reactive intermediate ubiquitous in sunlit aquatic environments. In the past years, there has been a steady increase in the number of publications reporting apparent singlet oxygen quantum yields (ΦΔ) of natural organic matter samples. Singlet oxygen quantum yields represent the number of 1O2 molecules produced per photon absorbed by a sensitizer. This parameter is required to predict the environmental fate of contaminants and biomolecules in sunlit surface waters and can also provide insights into dissolved organic matter photophysics. Despite this interest, there is a lack of reproducibility in 1O2 quantum yield measurements across research groups and publications. This problem originates from a combination of factors, including the intrinsically low ΦΔ values of natural samples, the complex chemical nature of the sensitizer, and the variability in experimental conditions and data analysis protocols. In this work, we present a critical evaluation of experimental techniques for ΦΔ measurements of natural organic matter samples. By estimating the errors associated with each empirical variable, we identify the rate of light absorption as the most sensitive parameter in ΦΔ determinations. This work highlights the need for shared guidelines and validation protocols for apparent quantum yield measurements of natural samples.

Critical evaluation of measurements approaches for apparent singlet oxygen quantum yields

ACS Spring Meeting 2021

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