Trace detection of NO and NO2 by photoionization and laser induced fluorescence techniques

The analytical capabilities of photoionization spectroscopy (PIS) and laser induced fluorescence (LIF) techniques have been evaluated to determine the relative merits of each technique for measurements of NO and NO2 at the pp b and sub-ppb level. For both techniques, excitation is accomplished via th e A-X (1,0) band of NO near 215 nm. For the ionization measurements, a (1 1) PIS scheme is utilized where NO molecules are photoionized by a second laser operating at 355 nm. Nitrogen dioxide (NO2) is determined by a photof ragmentation approach where NO is photofragmented from the parent molecule and then detected by PIS. Limits of detection by the PIS approaches are 0.0 5 ppb for NO in air and 6 ppb for NO2 in air. For LIF, fluorescence emissio n is measured via the A-X (0,1) band at 237 nm. Limits of detection by LIF are 0.2 ppb and 30 ppb for NO in N-2 and air, respectively. (C) 1999 Elsevi er Science B.V. All rights reserved.