Perfluorinated Sulfonic Acids Research Articles

Method for the determination of perfluorinated compounds (PFCs) in water by solid-phase extraction and liquid chromatography/tandem mass spectrometry (LC/MS/MS)

A solid phase extraction-liquid chromatography tandem mass spectrometry (SPE-LC/MS/MS) analytical method for the analysis of perfluorinated compounds (PFCs) in water is presented. The method incorporates a stable isotope internal standard (IS) for each target analyte added prior to sample collection. Method validation for perfluorinated carboxylic acids (PFCAs) (C4–C12), perfluorinated sulfonic acids (PFSAs) (C4, C6, and C8), and perfluorooctane sulfonamide (PFOSA) in laboratory Milli Q water evaluated the following: (1) method accuracy and precision over the concentration range 0.025 ng mL−1 to 25 ng mL−1; (2) internal standard calibration; (3) quantitation of mixed branched and linear isomers of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) with linear isomer calibration; (4) method minimum reporting levels (MRLs) (Shoemaker et al, http://www.epa.gov/nerlcwww/Method%20537_FINAL_rev1.1.pdf, and Winslow et al, Environ. Sci. Technol., 2006, 40, 281–288); and (5) 28 day holding time at the MRL, low, and mid range of the calibration range. IS calibration with IS addition to the sample bottle prior to sample collection demonstrated an overall method accuracy of at least 100 ± 10% with a precision of ±15% and a 28-day sample holding time at the MRLs for all target analytes. Method application to groundwater, production facility non-contact cooling water, and production facility wastewater treatment effluent samples demonstrated a method accuracy of at least 100 ± 19% with a precision of ±25% for all target analytes.

New Multi Acid Side-Chain Ionomers for Proton Exchange Membrane Fuel Cells

This work describes the modification of the sulfonyl fluoride precursor of perfluorinated sulfonic acids (PFSAs) by the conversion of the sulfonyl fluoride group to a bis sulfonylimide group. The usefulness of these new polymers for fuel cell applications includes novel proton exchange membranes, catalyst additives or tie layers designed to be thermally and chemically robust while operating within a fuel cell's harsh environment at higher temperatures.

Perfluoroalkyl sulfonic and carboxylic acids: A critical review of physicochemical properties, levels and patterns in waters and wastewaters, and treatment methods

Perfluorinated acids (PFAs) are an emerging class of environmental contaminants present in various environmental and biological matrices. Two major PFA subclasses are the perfluorinated sulfonic acids (PFSAs) and carboxylic acids (PFCAs). The physicochemical properties and partitioning behavior for the linear PFA members are poorly understood and widely debated. Even less is known about the numerous branched congeners with varying perfluoroalkyl chain lengths, leading to confounding issues around attempts to constrain the properties of PFAs. Current computational methods are not adequate for reliable multimedia modeling efforts and risk assessments. These compounds are widely present in surface, ground, marine, and drinking waters at concentrations that vary from pg L− 1 to μg L− 1. Concentration gradients of up to several orders of magnitude are observed in all types of aquatic systems and reflect proximity to known industrial sources concentrated near populated regions. Some wastewaters contain PFAs at mg L− 1 to low g L− 1 levels, or up to 10 orders of magnitude higher than present in more pristine receiving waters. With the exception of trifluoroacetic acid, which is thought to have both significant natural and anthropogenic sources, all PFSAs and PFCAs are believed to arise from human activities. Filtration and sorption technologies offer the most promising existing removal methods for PFAs in aqueous waste streams, although sonochemical approaches hold promise. Additional studies need to be conducted to better define opportunities from evaporative, extractive, thermal, advanced oxidative, direct and catalyzed photochemical, reductive, and biodegradation methods. Most PFA treatment methods exhibit slow kinetic profiles, hindering their direct application in conventional low hydraulic residence time systems.

Predicting the Congener-Specific Environmental Behaviour of Perfluorinated Acid Contaminants Using Semi-Empirical Computational Methods

AbstractPerfluorinated acids (PFAs) are contaminants detected worldwide in a range of abiotic and biotic environmental matrices. The two major classes of PFAs include the perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonic acids (PFSAs), both of which are considered persistent and potentially bioaccumulative. Current research and regulatory efforts are focussed on the straight-chain members of each PFA class and homologue group, primarily because these congeners are the major components of technical mixtures and are also available as pure standards. However, the numerous potential branched congeners in each PFA class represent a poorly understood family of environmental contaminants whose environmental and toxicological properties may be more important than the more prevalent straight-chain members. To help broaden the current understanding of PFA environmental fate and toxicology, semi-empirical computational methods were used predict fundamental physico-chemical properties of all potential C4 to C8 PCFA and PFSA congeners. Established quantitative structure-activity models for other multi-class emerging and legacy contaminants were applied to estimate key parameters related to the toxicology, environmental partitioning, and abiotic and biotic degradation mechanisms for each PFA class. The findings provide guidance for developing new analytical methods for separating and identifying PFAs in environmental and technical mixtures, prioritizing efforts on synthesizing authentic standards, and focussing toxicological studies on the congeners most likely to be of concern.

The Development of New Membranes for Proton Exchange Membrane Fuel Cells

Recent work at 3M has focused on the development of solvent cast proton exchange membranes (PEM's) for use in PEM fuel cells. These new membranes are a perfluorinated sulfonic acids based on a low molecular weight perfluorinated monomer and they exhibit excellent mechanical properties and chemical stability and high ionic conductivity. The low molecular weight of the monomer allows membranes with equivalent weight as low as 800 g/mole to have good mechanical properties when hydrated. Stabilizing additives in these membranes have been shown to improve the oxidative stability in Fenton's tests. Physical property, conductivity and fuel cell tests have been performed. When incorporated into membrane electrode assemblies, these new membranes have provided excellent performance and a greater than 15-fold increase in durability under accelerated fuel cell test conditions, compared with similar commercial PEM's.