Selective ultra-trace detection of NO and NO2 in complex gas mixtures using broad-bandwidth REMPI mass spectrometry

Abstract

In this paper we demonstrate the feasibility of ultra-trace resonance enhanced multiphoton ionization (REMPI) detection employing a small broad-bandwidth solid state laser system. The results reported here are compared with measurements carried out with a conventional excimer pumped dye laser combination. Mass selected broad-bandwidth REMPI spectra for the environmentally relevant nitrogen oxides NO and NO2 are presented. Tunable broad-bandwidth laser radiation with a spectral resolution of > 10 cm(-1) in the wavelength range 560-400 nm was employed for the detection of NO2. For NO detection, the range 230-224 nm was covered. Laser radiation was generated using an optical parametric oscillator pumped by an unseeded Nd:YAG laser. A mobile time-of-flight mass spectrometer equipped with an atmospheric pressure laser ionization source allowed for mass selective parent ion detection at m/z 30 for NO and m/z 46 for NO2. The limit of detection was 10 pptV for NO and 20 pptV for NO2. A selectivity of > 2000 for both compounds with respect to N2O5, organic nitrates and NO2 in the case of NO is reported. An improved laser system currently under construction is expected to provide detection limits below pptv mixing ratios for both nitrogen oxides in a 20 s integration interval.

Development of medium pressure laser ionization, MPLI. Description of the MPLI ion source

“…Results reported in a recent paper are promising [30]. It is shown that under limited rotational cooling conditions the efficiency of selected photo ionization processes in conjunction with broad-bandwidth laser excitation results in a similar performance with respect to sensitivity compared to the jet-cooling/narrow bandwidth excitation approach.…”

Autocatalytic reaction on low-dimensional substrates

“…On the other hand, when d > 2, the resulting curves are overlapped, hence no improvement is achieved. It should be underlined that the high sensitivity attained just for small concentrations of reactants makes this analytic technique very suitable for the determination of ultratrace amounts of reactants, which is of great experimental importance [29,30,31] …”

Development of a new Long Path Absorption Photometer (LOPAP) instrument for the sensitive detection of NO<sub>2</sub> in the atmosphere

“…Both coils have similar dimension than the HONO/O3-scrubber. The gas phase is sucked with a membrane pump through the stripping-coils, a security flask with electrical control, a Teflon membrane HONO (Milani and Dasgupta, 2001) and ozone interferences (Adema, 1979) by the Griess-Saltzman reaction are suppressed. NO 2 and other potential interferences are collected in the second stripping-coil (Channel 1), while potential interferences are measured in the third coil (Channel 2).…”

“…Spectroscopic methods such as Differential Optical Absorption Spectroscopy (DOAS) (Platt et al, 1979;Edner et al, 1993;Thornton et al, 2003), Laser Induced Fluorescence (LIF) (Thornton et al, 2000;Matsumoto et al, 2001Matsumoto et al, , 2006Dari-Salisburgo et al, 2009;Fuchs et al, 2010), Cavity Ring Down Spectroscopy (CRDS) (Mazurenka et al, 2003;Hargrove et al, 2006;Osthoff et al, 2006;Fuchs et al, 2009Fuchs et al, , 2010, Incoherent Broad Band Cavity Enhanced Absorption Spectroscopy (IBBCEAS) (Gherman et al, 2008;Wu et al, 2009;Fuchs et al, 2010), Cavity Attenuated Phase shift Spectroscopy (CAPS) (Kebabian et al, 2005(Kebabian et al, , 2008, Tunable Diode Laser Absorption Spectroscopy (TDLAS) (Gregory et al, 1990;Li et al, 2004;Herndon et al, 2004), and Resonance Enhanced MultiPhoton Ionization (REMPI) (Garnica et al, 2000;McKeachie et al, 2001) have been used for NO 2 detection, with some of them reaching very low detections limits (e.g. REMPI, LIF).…”