An evaluation of integrating techniques for measuring atmospheric nitrogen dioxide

Two integrating techniques for measuring ambient NO₂were evaluated. Both techniques involved quantitative collection of NO₂in a reagent coated cartridge, specifically triethanolamine (TEA)coated silica gel and diphenylamine (DPA)coated Florisil. The evaluation of these techniques consisted of laboratory and field studies. The laboratory studies of the TEA method indicated collection and reaction efficiencies of 100 and 90%, respectively. A positive interference occurred when O₃and NO were passed through the cartridge simultaneously. PAN was found to produce a 67% positive interference. The ambient concentrations determined using the TEA method were approximately a factor of two higher than those determined using TDLAS. For the DPA method the collection and reaction efficiencies were determined to be 100 and 64%, respectively. O₃produced a negative interference by reacting with the NO₂DPA products. PAN produced a 42% positive interference. A regression of the DPA versus TDLAS determined ambient NO₂concentrations yielded a slope of.91±.08 (r²=0.990.). Neither method was found suitable for network use in its present form.