ANALYSIS OF ALKYL NITRATES AND SELECTED HALOCARBONS IN THE AMBIENT ATMOSPHERE USING A CHARCOAL PRECONCENTRATION TECHNIQUE

A method has been developed to measure greater-than-or-equal-to C3 alkyl nitrates and C1-C2 halocarbons, such as perchloroethylene and bromoform, in ambient air. The method preconcentrates analytes on a 5-mg charcoal trap from multiliter volumes of air. Analytes are desorbed from the charcoal with a small volume of solvent and are analyzed by high-resolution gas chromatography with electron capture detection. Laboratory and field tests have been performed to evaluate method precision, analyte breakthrough, and compound recovery from the charcoal. Tests verified that the sampling/analytical system is free from artifact formation under clean to moderately polluted conditions, but further tests are required for areas of high concentrations of hydrocarbons, NO(x), and oxidants. The method allows measurement of halocarbons and greater-than-or-equal-to C3 alkyl nitrates at concentrations in the pptv range.