Sorbic
Acid as a Triplet Probe: Triplet Energy and
Reactivity with Triplet-State Dissolved Organic Matter via <sup>1</sup>O<sub>2</sub> Phosphorescence
Kyle J. Moor
Markus Schmitt
Paul R. Erickson
Kristopher McNeill
10.1021/acs.est.9b01787.s001
https://acs.figshare.com/articles/journal_contribution/Sorbic_Acid_as_a_Triplet_Probe_Triplet_Energy_and_Reactivity_with_Triplet-State_Dissolved_Organic_Matter_via_sup_1_sup_O_sub_2_sub_Phosphorescence/8636348
Sorbic acid (2,4-hexadienoic acid;
HDA) is commonly used as a probe
and quencher for triplet-excited chromophoric dissolved organic matter
(<sup>3</sup>CDOM*), an important transient species in natural waters,
yet much remains unknown about its reactivity with <sup>3</sup>CDOM*
and its triplet energy. To better understand the quenching behavior
of HDA, we measured HDA quenching rate constants for various humic
substance isolates and whole waters with singlet oxygen (<sup>1</sup>O<sub>2</sub>) phosphorescence and determined the triplet energy
of HDA. Low-temperature phosphorescence measurements determined the
triplet energy of HDA to be 217 kJ mol<sup>–1</sup>, whereas
a complementary method based on triplet quenching kinetics found a
triplet energy of 184 ± 7 kJ mol<sup>–1</sup>. Time-resolved <sup>1</sup>O<sub>2</sub> phosphorescence measurements yielded different
HDA quenching rate constants depending on the fitting method. Using
an approach that considered the reactivity of the entire triplet pool
produced values of (∼1–10) × 10<sup>8</sup> M<sup>–1</sup> s<sup>–1</sup>, while an approach that considered
only the reactivity of the high-energy triplets output higher rate
constants ((∼7–30) × 10<sup>8</sup> M<sup>–1</sup> s<sup>–1</sup>). In addition, the model based on high-energy
triplet reactivity found that ∼30–60% of <sup>3</sup>CDOM* is not quenched by HDA. Findings from this study provide a
more comprehensive view on the use of HDA as a probe for <sup>3</sup>CDOM*.
2019-06-20 00:00:00
Triplet-State Dissolved Organic Matter
Low-temperature phosphorescence measurements
triplet quenching kinetics
Time-resolved 1 O 2 phosphorescence measurements
3 CDOM
triplet energy
1 O 2
HDA quenching rate constants
reactivity