Analytical method validation for the determination of 2,3,3,3-tetrafluoropropene in air samples using gas chromatography with flame ionization detection.

A new low global warming refrigerant, 2,3,3,3-tetrafluoro propene, or HFO-1234yf, has been successfully evaluated for automotive air conditioning, and is also being evaluated for stationary refrigeration and air conditioning systems. Due to the advantageous environmental properties of HFO-1234yf versus HFC-134a, coupled with its similar physical properties and system performance, HFO-1234yf is also being evaluated to replace HFC-134a in refrigeration applications where neat HFC-134a is currently used. This study reports on the development and validation of a sampling and analytical method for the determination of HFO-1234yf in air. Different collection media were screened for desorption and simulated sampling efficiency with three-section (350/350/350 mg) Anasorb CSC showing the best results. Therefore, air samples were collected using two 3-section Anasorb CSC sorbent tubes in series at 0.02 L/min for up to 8 hr for sample volumes of up to 9.6 L. The sorbent tubes were extracted in methylene chloride, and analyzed by gas chromatography with flame ionization detection. The method was validated from 0.1× to 20× the target level of 0.5 ppm (2.3 mg/m(3)) for a 9.6 L air volume. Desorption efficiencies for HFO-1234yf were 88 to 109% for all replicates over the validation range with a mean overall recovery of 93%. Simulated sampling efficiencies ranged from 87 to 104% with a mean of 94%. No migration or breakthrough to the back tube was observed under the sampling conditions evaluated. HFO-1234yf samples showed acceptable storage stability on Anasorb CSC sorbent up to a period of 30 days when stored under ambient, refrigerated, or frozen temperature conditions.

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.

Estimation and validation of biomarker-based exposures for historical ammonium perfluorooctanoate.

Ammonium perfluorooctanoate (APFO) exposures were estimated for use in an occupational mortality study using detailed work histories of cohort members and an exposure reconstruction model developed from occupational information and serum PFO(-) data collected in 2004 as part of a cross-sectional health survey. Measured serum PFO(-) levels of the health survey participants were linked with the job title held by the individuals at the time of sampling. The median, range, and distribution of serum levels were calculated to determine the typical exposure intensity for each job title. High variability was observed in the serum levels of workers within the same job titles. In addition, working in many "APFO-use" jobs did not result in higher exposure than working in "no APFO-use" jobs. Each job title was then assigned to one of three relative APFO job exposure categories (low, medium, or high). Participants' length of time in their job was examined in relation to their serum PFO(-) level and found unlikely to contribute to misclassification of job titles within exposure categories. The mean of the serum PFO(-) measurements for each job exposure category served as the mean intensity factor. Subsequently, the job exposure categories were applied to all historical job titles of the mortality cohort based on their correspondence with job titles represented in the health survey. The resulting job exposure matrix was validated with additional historical blood data collected between 1979 through 2002 from voluntary participants in a separate biomonitoring program. The validation analyses showed general agreement between estimated and measured exposure, reflecting the within-job-title variability observed in measured serum levels used to classify job exposure.

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).