A method for the airborne measurement of PAN, PPN, and MPAN

An aircraft-based instrument for the measurement of peroxyacetic nitric anh ydride (PAN) and related compounds peroxypropionic nitric anhydride (PPN), and peroxymethacrylic nitric anhydride (MPAN) is described. The instrument functions by direct injection of a small sample (2 ambient cm(3)) into a wi de bore fused silica capillary gas chromatographic separation column with s ubsequent detection by electron capture. The efficiency of separation and e arly elution of water made possible a sampling frequency of once every 5 mi n. The selective destruction of PAN type compounds at 125 degreesC in actua l ambient samples showed that no interfering species were present. Calibrat ion of the instrument was accomplished by the total odd-nitrogen (NO) measu rement of air mixtures of high-purity PANs. Inflight calibrations of PAN in either thermally decomposed ambient air or dry zero air showed that the se nsitivity of the instrument to PAN was not affected by other matrix species such as carbon dioxide or water. The instrument response to PPN and MPAN r elative to that of PAN was consistent (within 5%) over the span of several months. The instrument response to PAN was linear up to 3.5 ppbv and the sl ope of the response versus [PAN] indicated a relative standard deviation of 2% over the course of a 30-day field study. The detection limits of the me thod for PAN and PPN were estimated to be 5 pptv (3s) based on the uncertai nty of peak detection. The overall accuracy of the PAN measurement was esti mated to be +/-(5 pptv+15%) in one campaign and +/-(5 pptv+20%) in others.