Abstract
A simple and reliable method is developed for routine analysis of atmospheric PPN at ppt level as well as PAN (peroxyacetyl nitrate). PPN was synthesized by ultraviolet photolysis of n-propyl nitrite vapor in oxygen in a Tedlar bag. The amount of PPN in the bag was calculated fromthe bands (9.58 μm) of the infrared spectrum. PPN in the air was collected by the U-shape Teflon trap [3mm (i. d.)× 30 cm (l.) tube packed with 0.3 g Teflon beads] immersed in dry ice-ethanol. PPN in the trap chilled with dry ice-ethanol is stable beyond two days, and the effect of desorption temperature on PPN decomposition in the trap can be ignored in the range of 20 to 50°C. The reliability of PPN values obtained from chromatograms was secured by the ECD-Absorber-ECD line connected to the exit of the GC-column. The absorber of the Teflon tube [2 mm (i. d.)× 30 cm (l.)] packed with 0.5 g of 10 KOH on Teflon beads (30-60 mesh) completely absorbes PAN and PPN for hundreds hours. The amount of PAN and PPN can be estimated from the difference between two ECD responses after the correction of the relative responses of the two ECD and the ECD loss (see Table 3). Atmospheric PPN concentration measured by this method was estimated to be about 11% of PAN at the site located on the edge of Tokyo Megalopolis Area. The detection limit of PPN was 10 ppt (10 × 10-12v/v) for 200 ml of air.
