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Use of Chiral Alcohols for Elucidating the Mode and Kinetics of Degradation of Fluorotelomer Compounds
Citation:
Washington, J., J. Ellington, AND T. Jenkins. Use of Chiral Alcohols for Elucidating the Mode and Kinetics of Degradation of Fluorotelomer Compounds. Presented at 34th Annual SETAC North America, Nashville, TN, November 17 - 21, 2013.
Impact/Purpose:
Presentation given at SETAC North America 34th in Nashville, TN (Nov 17-21, 2013)
Description:
Fluorotelomer polymers are the dominant product line of the fluorotelomer industry. Fluorotelomer polymers have been shown to degrade under environmental conditions to form numerous fluorotelomer and perfluorinated monomers that are of environmental and toxicological concern; however, because fluorotelomer polymers are notoriously difficult to experiment with, details of the rates and paths of degradation for these major market-place polymers remain ill-defined. In an effort to help elucidate the degradability of fluorotelomer polymers and their monomers, we studied the degradation of primary fluorotelomer alcohols (n-FTOHs), both mass-labeled and unlabeled, in selected soils in which we monitored loss of n-FTOH and ingrowth of numerous degradation products using a GC/MS system operated in positive chemical-ionization mode and an LC/MS/MS system operated in negative electrospray-ionization mode. Among these degradation products, we quantitated sec fluorotelomer alcohols (s-FTOHs) which have a chiral center, as well as determining their enantiomeric ratio using a chiral capillary column. Informed by these experiments, we embarked on experiments with commercial fluorotelomer polymers in soil. Here we report observations of changes in s-FTOH concentration and enantiomeric ratio. Variables in the experiments included incubation time, n-FTOH and s-FTOH homologue length, incubating soil, and soil-spiking mode. In a soil that was spiked with 8:2n-FTOH, ingrowth of one enantiomer of 7:2s-FTOH dominated, strongly supporting that the generation/loss of 7:2s-FTOH is biologically mediated. In contrast, when the same soil was spiked with 10:2n-FTOH, in at least one incubation series, no 9:2s-FTOH was observed. When 7:2s-FTOH was spiked into soil directly, the alcohol was lost during incubation, but the enantiomeric ratio remained close to racemic suggesting that the loss was not biologically mediated, perhaps a volatilization or irreversible sorption artifact. It is noteworthy that within test soil and incubation time, the enantiomeric ratio generally remains coarsely internally consistent among separate microcosms, so these data support the notion that modes of fluorotelomer biotransformation remain internally consistent between microcosms for the periods of incubation we have completed.
