Unusual Fragmentations of Silylated Polyfluoroalkyl Compounds Induced by Electron Ionization

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Mass Spectrometry

Background:

• Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants with significant analytical challenges.
• Accurate identification of PFAS is crucial for environmental monitoring and risk assessment.
• Existing mass spectral libraries may lack comprehensive data for PFAS identification.

Purpose of the Study:

• To investigate the electron ionization (EI) mass spectra of trimethylsilyl (TMS) derivatized fluorinated alcohols and carboxylic acids.
• To improve the identification of PFAS compounds within the NIST Mass Spectral Reference Library.
• To elucidate unique fragmentation pathways of PFAS derivatives.

Main Methods:

• Analysis of EI mass spectra of TMS-derivatized fluorinated alcohols and carboxylic acids.
• Utilized NIST software tools and high-resolution time-of-flight mass spectrometry (TOF-MS) for quality assurance.
• Performed MS2 experiments and full scan analyses on derivatives with varying methylene group lengths.

Main Results:

• Observed distinct fragmentation patterns for TMS-derivatized fluorinated alcohols, characterized by the loss of fluorinated silyl groups, unlike non-fluorinated analogs.
• Consistently detected a novel [M-111]+ ion in compounds with three methylene groups between the hydroxyl and CF2 unit.
• Confirmed the origin and elemental composition of fragment ions using advanced analytical techniques.

Conclusions:

• The study elucidates a unique fragmentation pathway involving a five-membered ring intermediate in TMS-derivatized PFAS.
• These findings enhance the understanding of PFAS fragmentation mechanisms.
• Improved identification of PFAS in analytical workflows is supported, contributing to better environmental analysis.