Analysis of perfluorocarboxylic acids in air

Perfluorocarboxylic acids have been used in limited but important applications, such as in the production of fluoroelastomers and as components of fire-fighting foams. A method for the measurement of perfluorocarboxylic acids of different chain lengths in air is presented. Chain lengths tested included those having 8, 9, 10, 11, and 13 carbon atoms. Occupational Safety and Health Administration (OSHA) Versatile Sampler airtubes with glass fiber filter, XAD-4 resin, and polyurethane foam were fortified with analyte at levels corresponding to 0.1, 0.5, 1.0, and 2.0 times the level representing a 0.01 mg/m3 analyte air concentration sampled for 8-hour period with an airflow rate of 1 L/min. Airtube sections were extracted with acetone. Analysis of analyte in airtube fraction extracts was by HPLC/MS using ammonium acetate in water and methanol mobile phase and single ion monitoring for quantification. The lower limit of quantification for the HPLC/MS was set at 0.0001 mg/m3 for each analyte. Total recoveries of analytes within National Institute for Occupational Safety and Health (NIOSH) guidelines of +/- 25% of the true value were obtained at three different atmospheric conditions: ambient, cool/dry, and warm/humid conditions. The maximum loading with acceptable recovery of each analyte was 9600 ng (48000 ng total) for the ambient and warm/humid conditions. The maximum loading with acceptable recovery was 4800 ng (24000 ng total) for the cool/dry condition. The ammonium salt of the eight-carbon perfluorocarboxylic acid, ammonium perfluorooctanoate, was similar to the parent acid in behavior at the ambient condition. Hydrohexadecafluorononanoic acid was tested as a possible surrogate standard for the method, and it was found unsuitable for use because of variable recoveries. Stability studies were completed, and the perfluorocarboxylic acid analytes were stable in airtube samplers for up to 14 days at either ambient or refrigerated condition.