Perfluoroalkyl acids degradation

Abstract In the past years, elucidation of transformation products of per- and polyfluorinated chemicals (PFC) has been a task frequently approached by analytical chemists. PCT, such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are persistent and thus, the analytical quest to detect transformation products has failed so far. Their prominence as contaminants is mainly due to their extreme persistence, which is linked to their perfluoroalkyl chain length. Molecules that are less heavily fluorinated can show very complex metabolic behavior, as is the case for fluorotelomer alcohols. These compounds are degraded via different but simultaneous pathways, which produce different stable metabolites. Biotransformation processes of PFC may occur when these compounds enter the environment, and thus known and unknown PFC may be generated in these compartments. Therefore, it is essential to determine metabolic pathways of such compounds in order to entirely understand their fate in the environment. This chapter summarizes methodological approaches and instmmental setups which have been implemented in biotransformation studies of PFC and focuses on mass spectrometric methods and the separation techniques coupled to the mass spectrometer (MS). Valuable MS approaches that have not been frequently used in studies on PFC are presented as well. Since compounds carrying C-F bonds exhibit unique properties, these will be initially presented to address the meaning of these properties both for analytical tasks and for the setup of biotransformation experiments. 

Electrophilic reactions are not usually observed, e.g., it was not possible to obtain a haloacetate from F5SCH=CH2 under the same conditions (acetic acid, bromine, mercury acetate) where perfluoroalkyl-substituted ethylenes are known to yield haloacetates. An exception is the rather easy (47) addition of SO3 to F SCH=CF2> although a significant amount of by-product is formed, one of which is formed in an intricate reaction that leads to the degradation of the SF5-group (48). 

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