INTERCOMPARISON OF NO2 MEASUREMENT TECHNIQUES

1) The photolysis/chemiluminescence (PC) instrument, 2) the tunable diode laser absorption spectrometer (TDLAS), and 3) the Luminox instrument. Calibrated mixtures of NO2 in air and NO2 with possible interferants (HNO3, peroxyacetyl nitrate (PAN), H2 O2, n-propyl nitrate, and O3) were provided in simultaneous tests. 1) For NO2 levels above 2 parts per billion by volume (ppbv), similar results were obtained for all instruments; 2) below 2 ppbv, the expected interferences from ozone and PAN influenced the NO2 measurements made using the Luminox instruments; 3) the ozone interference on the Luminox instruments was removed by an ozone scrubber placed in the sampled air stream of the Luminox instrument; 4) although no interferences were identified for the TDLAS technique, care must be taken in the data analysis near (or below) the detection limit for the instrument; 5) no interferences or artifacts were found for the final results reported by the PC technique. -from Authors