Abstract
A cryogenic collection method is developed for routine use in the analysis of atmospheric peroxyacetyl nitrate (PAN) with a gas chromatograph (GC)-electron capture detector (ECD). Six tiubes were tested for a collecting trap by using liquid oxygen as a refrigerant. These tubes were composed of four-Teflon tube [1.0-3.0 mm (i.d.), 30-200 cm (1.)] packed with Teflon beads or Teflon wool or unpacked, a Pyrex glass tube [3mm (i.d.), 30 cm (1.)] packed with Pyrex glass beads, and a open stainless steel tube [0.8 mm (i.d.), 300 cm (1.)] The Teflon tube (3 mm × 30 cm) packed with 0.3 g Teflon beads (‘A’ tube) was found to be most suitable for a collecting trap by reasons of high recovery of PAN, ease of preparation and handling conveniences. The effect of desorption temperature on PAN decomposition in the ‘A’ tube can be ignored in the range of 0× to 70×C.
The break-through volume of the ‘A’ tube for PAN is more than 2.5 liter at the temperature of liquid oxygen temperature, thus the cryogenic collection method connecting to GC-ECD allows the determination of PAN at several tens ppt (parts per trillion, 10-12 v/v) with sufficient sensivity and adequate precision. PAN in the ‘A’ tube chilled with liquid oxygen is stable beyond forty -eight hours, then, this collection method also allows the air sampling for PAN at the site far from a laboratory. Diurnal variation of atmospheric PAN was measured by GC-ECD with the cryogenic collection method and with the direct injection method at the same place for two days. Any practical difference was not observed between the PAN concentrations by these two method.
