A long-term sampling method for the collection of C2-C4 fatty acids in air

Abstract

A long-term sampling method for the collection of C2-C4 fatty acids in air has been evaluated. When the determination of total acids is desired, acetic, propionic and butyric acids are adsorbed on silica gel and desorbed with acetone and water. They are then determined by titration with sodium hydroxide. When a more selective method of analysis is desired, the acids are desorbed from silica gel with 1% aqueous formic acid and determined by gas chromatography. Approximately 30 mg of C2-C1 fatty acid has been collected on commercially available 780-mg silica gel tubes at a relative humidity of 63% over a 7.5-hr period without breakthrough. The desorption efficiency for the C2-C4 fatty acids using acetone and water was determined to be greater than 98%, and the desorption efficiencies for acetic, propionic and butyric acids using 1 % aqueous formic acid were 94, 88 and 85%, respectively.