Determination of Peroxyacetylnitrate (PAN) in Unpolluted Areas

Abstract

PAN is not only important as toxic product of photochemical pollution but may also act as an important reservoir for nitrogen oxides outside polluted areas.

However, only very few measurements of PAN in unpolluted areas have been reported in the literature, mainly as a result of the lack of simple, reliable and sufficiently sensitive techniques for the measurements of PAN in background air.

In our paper we will describe a completely automatic gas chromatographic system. Without enrichment it allows the determination of PAN with a lower limit of detection of ≈ 10ppt. Combined with an adsorptive enrichment procedure at low temperature detection limits of less than 1 ppt are possible. At these low concentrations, a complete separation from possible interfering atmospheric constituents (e.g. halocarbons) is necessary. This is achieved by separation on a 1 m long glass column, i.d. 2 mm, packed with 5% PEG 400 on Chromosorb WHP 80/100 mesh at ambient temperature. For field measurements-especially for in situ measurements on board of airplanes-a special light weight gas chromatograph with a peltier cooled oven was developed.

Key Words:

• Peroxyacetyl nitrate measurements by gas chromatography
• adsorptive enrichment of PAN
• automatic instrument for PAN measurement at ppt levels