Recent developments in trace analysis of poly- and perfluoroalkyl substances.

Recent developments, improvements, and trends in the ultra-trace determination of per- and polyfluoroalkyl substances (PFASs) in environmental and human samples are highlighted and the remaining challenges and uncertainties are outlined and discussed. Understanding the analytical implications of such things as adsorption of PFASs to surfaces, effects of differing matrices, varying PFAS isomer response factors, potential bias effects of sampling, sample preparation, and analysis is critical to measuring highly fluorinated compounds at trace levels. These intricate analytical issues and the potential consequences of ignoring to deal with them correctly are discussed and documented with examples. Isomer-specific analysis and the development of robust multi-chemical methods are identified as topical trends in method development for an ever-increasing number of PFASs of environmental and human interest. Ultimately, the state-of-the-art of current analytical method accuracy is discussed on the basis of results from interlaboratory comparison studies.

Understanding potential exposure sources of perfluorinated carboxylic acids in the workplace.

This paper integrates perspectives from analytical chemistry, environmental engineering, and industrial hygiene to better understand how workers may be exposed to perfluorinated carboxylic acids when handling them in the workplace in order to identify appropriate exposure controls. Due to the dramatic difference in physical properties of the protonated acid form and the anionic form, this family of chemicals provides unique industrial hygiene challenges. Workplace monitoring, experimental data, and modeling results were used to ascertain the most probable workplace exposure sources and transport mechanisms for perfluorooctanoic acid (PFOA) and its ammonium salt (APFO). PFOA is biopersistent and its measurement in the blood has been used to assess human exposure since it integrates exposure from all routes of entry. Monitoring suggests that inhalation of airborne material may be an important exposure route. Transport studies indicated that, under low pH conditions, PFOA, the undissociated (acid) species, actively partitions from water into air. In addition, solid-phase PFOA and APFO may also sublime into the air. Modeling studies determined that contributions from surface sublimation and loss from low pH aqueous solutions can be significant potential sources of workplace exposure. These findings suggest that keeping surfaces clean, preventing accumulation of material in unventilated areas, removing solids from waste trenches and sumps, and maintaining neutral pH in sumps can lower workplace exposures.

Development and validation of a wipe test method using liquid chromatography with tandem mass spectrometry for the determination of Perfluorooctanoate (PFO) on various surfaces.

Perfluorooctanoate (PFO) is the anion of perfluorooctanoic acid. As the ammonium salt, PFO has been used for 50 years as a processing aid in the commercial production of perfluorinated and highly fluorinated polymers. To assess the effectiveness of industrial hygiene controls in processes involving PFO products and intermediates, a wipe test was developed and validated to determine quantitatively the PFO concentration on six surfaces: stainless steel, polycarbonate, Formica, butyl acid suit material, laminated disposable suit material, and a painted surface. Acceptable recovery and precision results were obtained for nonporous surfaces, such as stainless steel, polycarbonate, Formica, acid suit material, and painted surfaces on a 10-cm x 10-cm surface. The analytical method was evaluated over a range of 1 to 23 ng/cm2, or 100 to 2300 ng/100 cm2. The reporting limit for the method was 100 ng/wipe.

A method for the low-level (ng/g) determination of perfluorooctanoate in carpet by LC-MS-MS using matrix extracted standards.

Fluorotelomer-based acrylic polymers are applied to the surface of carpet to impart oil, stain, and water repellence properties. Concerns that fluorotelomer-based polymers are a possible source of "low level" exposure to humans, coupled with their widespread use have prompted the need to develop a method to detect and measure perfluorooctanoate (PFO) in carpet. A liquid chromatography tandem mass spectrometry method for the determination of PFO in carpet using a dual labeled 13C-perfluoroctanoic acid (13C-PFOA) internal standard is successfully developed and validated. Levels of PFO are determined using a gradient, reversed-phase high-performance liquid chromatography (HPLC) method with acetic acid acidified water-methanol, separated on a 50 mm Phenomenex Synergi Polar RP column. Ions monitored are 413 (parent) and 369 (daughter) for PFO and 415 (parent) and 370 (daughter) for dual labeled 13C-PFOA internal standard. Accuracy and precision over three days for 5 to 900 ng/g PFO in carpet ranged from 2.4% to 7.6% and 3.7% to 14.1%, respectively. Overall extraction efficiency for samples (n=30) fortified with 13C-PFOA at 20 ng/g and perfluorooctanoic acid (PFOA) at 5, 50, and 500 ng/g is 98.9%+/-8.1%. Specificity of the method was evaluated with two different carpet samples.

Transport of ammonium perfluorooctanoate in environmental media near a fluoropolymer manufacturing facility.

In order to understand better the pathways for transport of ammonium perfluorooctanoate (APFO) from a point source, a focused investigation of environmental media (water and soil) near a fluoropolymer manufacturing facility (Site) was undertaken. Methods were developed and validated at 2 microg kg(-1) [the limit of quantitation (LOQ)] in soil, and at 50 ng l(-1) in water. Environmental media were sampled from a public water supply well field located north of the Site, across a river. The data suggest that APFO air emissions from the Site are transported to the well field, deposited onto the soil, and then migrate downward with precipitation into the underlying aquifer.

Vapor pressure determinations of 8-2 fluorortelomer alcohol and 1-H perfluorooctane by capillary gas chromatography Relative retention time versus headspace methods.

Two distinctly different capillary gas chromatographic methods were used to determine the vapor pressure of 8-2 fluorotelomer alcohol (8-2 FTOH) and 1-H perfluoroheptane at several temperatures. For measurements employing the relative retention-time method, a short polymethylsiloxane column was used from 25 to 65 degrees C. For the 8-2 FTOH, hydrocarbon alcohols and perfluoroalcohols were used as reference standards. For 1-H perfluoroheptane, hydrocarbons were used as reference standards. Vapor pressure estimates could differ by as much as an order of magnitude compared to published results determined by other (nonchromatographic) methods. This variance may be a function of solvent-solute interactions within the gas chromatographic column and the infinite dilution assumption, both used in the relative retention method. For comparison, data were also gathered using headspace gas chromatography (GC) with atomic emission detection (AED). The results from this novel GC/AED method were consistent with prior nonchromatographic results. A discussion of why headspace is the preferred technique for the determination of vapor pressure for fluorinated compounds is presented.

A method for the low-level (ng g(-1)) determination of perfluorooctanoate in paper and textile by liquid chromatography with tandem mass spectrometry.

The determination of perfluorooctanoate (PFO) in articles of commerce has become increasingly important to understand if treated products are a possible source of PFO. An LC-MS/MS method for the determination of PFO in paper and textile using a dual labeled 13C-PFOA internal standard was successfully developed and validated. Residues of PFO were determined using an isocratic, reversed-phase high-performance liquid chromatography (HPLC) method with an ammonium acetate/methanol buffer. Ions monitored were 413 (parent) and 369 (daughter) for PFO and 415 (parent) and 370 (daughter) for dual labeled 13C-PFOA internal standard. As a precaution against ubiquitous PFO that occasionally occurs in mobile phase or instrument components, two Hypercarb cartridges (4 mm) were placed before the HPLC injector. Any PFO that was captured by the cartridges was removed before each injection by flushing the system with 100% methanol prior to equilibration with the isocratic mobile phase. Overall recovery and standard deviation over a 3 day validation regimen for samples (n=54-55) fortified with PFOA at 5, 50, and 200 ng g(-1) were 114+/-4.9% for textile and 110+/-7.6% for paper. The results also established a limit of detection (LOD) of 1 ng g(-1) in textile and 2 ng g(-1) in paper based upon S/N of the 5.0 ng g(-1) fortification versus the untreated paper and textile.

Thermal degradation of fluorotelomer treated articles and related materials.

This study reports the first known studies to investigate the thermal degradation of a polyester/cellulose fabric substrate ("article") treated with a fluorotelomer-based acrylic polymer under laboratory conditions conservatively representing typical combustion conditions of time, temperature, and excess air level in a municipal incinerator, with an average temperature of 1000 degrees C or greater over approximately 2s residence time. The results demonstrate that the polyester/cellulose fabric treated with a fluorotelomer-based acrylic polymer is destroyed and no detectable amount of perfluorooctanoic acid (PFOA) is formed under typical municipal incineration conditions. Therefore, textiles and paper treated with such a fluorotelomer-based acrylic polymer disposed of in municipal waste and incinerated are expected to be destroyed and not be a significant source of PFOA in the environment.

Partitioning and removal of perfluorooctanoate during rain events: the importance of physical-chemical properties.

The potential for airborne emissions to undergo long-range transport or to be removed from the atmosphere is influenced by their physical-chemical properties. When perfluorooctanate (PFO) enters the environment, its physical-chemical properties can vary significantly, depending on whether it exists as an acid, a salt, or a dissociated ion. A summary of the physical-chemical properties of the three most likely environmental states: ammonium perfluorooctanoate (APFO), perfluorooctanoic acid (PFOA) and the dissociated perfluorooctanoate anion (PFO(-)) is presented to illustrate the distinct environmental properties of each. The most volatile species, PFOA, is shown to have a pH-dependent air-water partitioning coefficient (K(aw)). The variability of K(aw) with pH influences the potential for vapor formation from aqueous environments, including rain events. Using the pH-dependent K(aw) and measured rain and air concentrations, it is shown that vapor-phase PFOA is not likely to be present above measurable levels of 0.2 ng m(-3) (12 parts per quadrillion v/v) during a rain event. Because rain concentrations determined in this work are comparable to measurements in other parts of North America, it is unlikely that rain events are a significant source of vapor-phase PFOA for the general North American region. It is shown that PFOA exists primarily in the particle phase in ambient air near direct sources of emissions and is efficiently scavenged by rain droplets, making wet deposition an important removal mechanism for emissions originating as either PFOA or APFO. Washout ratios of particle-associated PFO were determined to range between 1 x 10(5) and 5 x 10(5), in the same range as other semi-volatile compounds for which wet deposition is an important mechanism for atmospheric removal and deposition onto soils and water bodies.

Efficient "total" extraction of perfluorooctanoate from polytetrafluoroethylene fluoropolymer.

To determine the optimum conditions for the complete extraction of perfluorooctanoate (PFO) from polytetrafluoroethylene fluoropolymers, sample preparation and pressurized solvent extraction (PSE) conditions were investigated. Solvent extraction temperature, solvent residence time, relaxation time between extractions, and the effects of heating before PSE showed that methanol at 150 degrees C extraction temperature and a 12 min solvent residence time were the most efficient conditions. Preheating the polymer before extraction at 150 degrees C for 24 h significantly enhanced the quantity of PFO removed. Heating above 150 degrees C resulted in loss of PFO. PFO was determined by liquid chromatography with tandem mass spectrometry.

Determination of perfluorooctanoic acid (PFOA) extractable from the surface of commercial cookware under simulated cooking conditions by LC/MS/MS.

Salts of pentadecafluorooctanoic acid (PFOA) are polymerization aids used in the manufacture of fluoropolymers; one of the applications of fluoropolymers is the coating of metal cookware products. A method was developed to determine if PFOA might be present in and extracted from the surface of commercial frying pans coated with a DuPont fluoropolymer under simulated cooking conditions. Commercial grade cookware was obtained, then extracted with water and ethanol/water mixtures at 100 and 125 degrees C, and the resulting extracts were analyzed by liquid chromatography tandem mass spectrometry (LC/MS/MS). Detection and quantification limits as low as 100 pg cm(-2) were demonstrated. None of the fluoropolymer treated cookware samples analyzed showed detectable levels of PFOA when extracted under simulated cooking conditions.

Comparison of pressurized solvent and reflux extraction methods for the determination of perfluorooctanoic acid in polytetrafluoroethylene polymers using LC-MS-MS.

Both pressurized solvent extraction (PSE) and reflux extraction in various solvents were used to select the most efficient system for the determination of the quantity of perfluorooctanoic acid (PFOA) present in polytetrafluoroethylene polymers. After evaporating the solvent, PFOA was determined using liquid chromatography tandem mass spectrometry. Ethanol, water and methanol gave comparable results and were shown to be good solvents for this extraction. Acetonitrile was a reasonable solvent using the reflux extraction method, but not with PSE. Chloroform resulted in poor recovery for both extraction methods. PSE proved to be the more efficient extraction method.

Method for the determination of perfluorooctanoic acid in air samples using liquid chromatography with mass spectrometry.

Perfluorooctanoic acid is a completely fluorinated carboxylic acid that is usually used in the ammonium salt form as a processing aid in the production of many fluoropolymers and fluoroelastomers. Ammonium perfluorooctanoate readily dissociates in water to give the ammonium and perfluorooctanoate ions. Perfluorooctanoate has been reported to be present in low levels in human serum in the United States and Europe. This study reports on the development and validation of a method for the determination of perfluorooctanoic acid in air samples. This method uses the Occupational Safety and Health Administration (OSHA) Versatile Sampler (OVS) with a nominal 0.3 micro m filter and polystyrene resin sorbent (XAD-2 or XAD-4) followed by determination of the perfluorooctanoate anion by liquid chromatography mass spectrometry. The method was validated in the range of 0.474 to 47.4 microg/m3 for a 480-L sample. Breakthrough studies showed samples could be collected at 1 L/min for 24 hours or at 15 L/min up to 8 hours without breakthrough. Extract storage stability tests showed that sample extracts in methanol remain stable in glass autosampler vials for up to 13 days following initial injection. Perfluorooctanoic acid stability on OVS tubes was unaffected at both refrigerated and ambient temperatures. The overall average retention efficiency was 92.1% with a pooled RSD95 of 5.8% at five concentration levels (0.474 microg/m3 to 47.4 microg/m3).

Vapor pressure and intramolecular hydrogen bonding in fluorotelomer alcohols.

Vapor pressure and aqueous solubility are important parameters used to estimate the potential for transport of chemical substances in the atmosphere. For fluorotelomer alcohols (FTOHs), currently under scrutiny by environmental scientists as potential precursors of persistent perfluorocarboxylates (PFCAs), vapor pressure is the more significant property since these compounds are only very sparingly soluble in water. We have measured the vapor pressures of a homologous series of fluorotelomer alcohols, F(CF2CF2)nCH2CH2OH (n = 2-5), in the temperature range 21-250 degrees C by three independent methods: (a) a method suitable for very low vapor pressures at ambient temperatures (gas-saturation method), (b) an improved boiling point method at controlled pressures (Scott method), and (c) a novel method, requiring milligram quantities of substance, based on gas-phase NMR, a technique largely unfamiliar to chemists and holding promise for studies of relevance to environmental chemistry. The concordant values obtained indicate that recently published vapor pressure data overestimate the vapor pressure at ambient temperature, and therefore the volatility, of this series of fluorinated compounds. It was suggested that substantial intramolecular -O-H...F- hydrogen bonding between the hydroxylic proton and the two fluorines next to the ethanol moiety was responsible for their putative high volatility. Therefore, we have used gas-phase NMR, gas-phase FTIR, 2D NMR heteronuclear Overhauser effect measurements, and high-level ab initio computations to investigate the intramolecular hydrogen bonding in fluorotelomer alcohols. Our studies unequivocally show that hydrogen bonding of this type is not significant and cannot contribute to and cause unusual volatility. The substantially lower vapor pressure at ambient temperatures than previously reported resulting from our work is important in developing a valid understanding of the environmental transport behavior of this class of compounds.