Semivolatile long chain C6–C17 alkyl nitrates as trace compounds in air

The analytical chemistry of long chain alkyl nitrates with carbon numbers up to 26 is reported for the first time. The thermolabile long chain alkyl nitrates can be analysed by capillary gas chromatography on short columns (5–10 m) with thin films (0,1–0,25pm). The short column technique combined with on-column injection and the use of hydrogen at high flow rates prevents the thermal degradation of the thermolabile semivolatile organonitrates during the GC separation. HRGC/ECD, and HRGC/MSD using 46 amu as the signal reveal a standard pattern of isomeric organonitrates surprizingly up to only C17 in semirural air. The concentrations decrease continously from 7,3 ng Nm−3 corresponding to 1,11 pptv for the hexyl nitrates to 1,7 ng NM−3 corresponding to 0,15 pptv for the tetradecyl nitrates. No semivolatile alkyl nitrates could be detected in particulates (≥2 micron) collected by a glass fibre filter. Alkyl nitrates are known as reservoir species of NO/NO2 in air. Their biological potential is also well established. Long chain alkyl nitrates form lipophilic carriers for NOx and therefore nitric acid and nitrate ions.