Development of a Gas Chromatograph for Trace Level Measurement of Peroxyacetyl Nitrate using Chemical Amplification

A gas chromatographic technique for trace level detection of peroxyacetyl nitrate (PAN) that relies on postcolumn chemical amplification as a means of improving the detection limit has been developed. The GC detector is based on luminol chemiluminescence detection of NO₂. PAN eluting from the chromatographic column is thermally decomposed, resulting in a free-radical chain reaction in which NO is converted to NO₂, using CO as a chain carrier. The system operates at optimized carrier gas NO and CO concentrations of 6 ppm and 8%, respectively. Under these conditions, the experimentally determined chain length (NO₂ detected per PAN injected) for [PAN] < 1 ppb is 180 ± 20. The instrument is found to exhibit a slightly nonlinear response to PAN concentrations, in the range 0.05-3 ppb, based on comparison with a GC-ECD. The chemical amplification GC was compared against a series of ambient air PAN measurements conducted using a GC-ECD instrument in December 1992 at a rural Ontario site. For ambient PAN concentrations ranging between ∼0.04 and 0.5 ppb the average difference between the chemical amplification GC and the GC-ECD was ±18%. This technique offers a sensitive method for trace level ambient PAN measurement without sample preconcentration.