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 approximately 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.