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Direct Observation of Photochemical Free Radical Production from the Sunscreen 2‐Phenylbenzimidazole‐5‐Sulfonic Acid via Laser‐Interfaced Mass Spectrometry
Author(s) -
Wong Natalie G. K.,
Berenbeim Jacob A.,
Dessent Caroline E. H.
Publication year - 2019
Publication title -
chemphotochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.13
H-Index - 18
ISSN - 2367-0932
DOI - 10.1002/cptc.201900149
Subject(s) - chemistry , mass spectrometry , photochemistry , dissociation (chemistry) , photosensitizer , molecule , photodissociation , excited state , deprotonation , fragmentation (computing) , organic chemistry , ion , chromatography , physics , nuclear physics , computer science , operating system
The common sunscreen molecule 2‐phenylbenzimidazole‐5‐sulfonic acid (PBSA) is studied in its gas‐phase deprotonated form ([PBSA‐H] − ) for the first time as an important step in achieving a better understanding of its behavior as a photosensitizer. UV laser‐interfaced mass spectrometry is employed, revealing that [PBSA‐H] − photofragments into three ionic products ( m/z 208, 193, and 80) with distinctive wavelength‐dependent production profiles. Both the m/z 208 and 80 channels produce associated neutral free radical species. Collision‐induced dissociation is performed on [PBSA‐H] − , showing that its hot ground‐state dissociates only into m/z 193 (statistical fragment). Therefore, the m/z 208 and 80 fragments which are produced strongly through the UVA/UVB are characterized as non‐statistical photofragments associated with non‐ergodic excited‐state decay. Our observation of non‐statistical photofragments reveal that [PBSA‐H] − is not behaving as a model sunscreen molecule. Further, our results indicate that the T 1 state, associated with photosensitization, decays with direct free radical production.