Direct Observation of Photochemical Free Radical Production from the Sunscreen 2‐Phenylbenzimidazole‐5‐Sulfonic Acid via Laser‐Interfaced Mass Spectrometry

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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 T1 state, associated with photosensitization, decays with direct free radical production.
Original languageEnglish
Number of pages7
Early online date12 Aug 2019
Publication statusE-pub ahead of print - 12 Aug 2019

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  • Free radicals
  • Photolysis
  • Photosensitizer
  • Sunscreen Molecules

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