Comparison of a chemiluminescent and a tunable diode laser absorption technique for the measurement of nitrogen oxide, nitrogen dioxide, and nitric acid

Comparisons were made between measurements of NO, NO sub(2), and HNO sub(3) made with an NO + O sub(3) chemiluminescence (CL) system and a tunable diode laser absorption spectrometer system. Good agreement was found for NO and NO sub(2) calibrations using synthetic air mixtures in the laboratory and in the field. Good agreement was also found for NO measurements in ambient and captive downtown Los Angeles air. Interferences with the CL measurements of NO sub(2) in ambient and captive air, primarily from PAN, were revealed by the comparison. Reasonable agreement was obtained for HNO sub(3) captive air, but the CL measurements in ambient air showed considerable variance due to fluctuating local NO sub(x) sources. Since both techniques have response times of less than 5 min, the temporal behavior of the three gases was observed in some detail.