A thermal dissociation–chemical ionization mass spectrometry (TD‐CIMS) technique for the simultaneous measurement of peroxyacyl nitrates and dinitrogen pentoxide

Abstract

[1] We have developed a thermal dissociation-chemical ionization mass spectrometry (TD-CIMS) technique for fast measurements of a series of peroxyacyl nitrates and dinitrogen pentoxide. Thermally generated acylperoxy radicals react with I À to produce a carboxylate ion that is unique for each parent species. NO 3 resulting from the decomposition of N 2 O 5 reacts with I À to form NO 3 À. The measurement technique was verified for PAN and PPN during an informal comparison with a gas chromatograph (GC) equipped with an electron capture detector (ECD) in Boulder, Colorado, during October 2002. Good agreement was obtained between the two instruments with R 2 = 0.91 for PAN (n = 657) and R 2 = 0.89 for PPN (n = 655). Detection limits of 7 pptv and 4 pptv were determined for PAN and PPN, respectively, for a 1 s integration period and a signal-to-noise ratio of 3. The TD-CIMS simultaneously detected ambient PiBN and N 2 O 5 + NO 3 in addition to PAN and PPN during the intercomparison period. We estimate a detection limit of 3 pptv in 1 s for PiBN. PnBN would be detected at the same mass, so we cannot rule out a contribution from PnBN to our PiBN estimate. Sensitivity to MPAN was found to be lower than to PAN in laboratory experiments, but a detection limit of 10 pptv can still be achieved by integrating for 15 s. Assuming the same sensitivity as for PAN, the detection limit for the sum of N 2 O 5 and NO 3 was estimated to be 12 pptv in 1 s. The fast time response of the TD-CIMS combined with a sensitivity and limit of detection comparable to the GC/ECD make this a promising technique for PAN flux measurements by eddy covariance. PAN uptake by different types of vegetation could be important input for global and regional ozone models, and PAN deposition to snow is of interest in polar regions.

A Chemical Ionization Mass Spectrometer for ambient measurements of Ammonia

“…1a). The third part of the CIMS (vacuum region) is similar to that of the Georgia Tech NH 3 -CIMS (Nowak et al, 2006(Nowak et al, , 2007 and of the H 2 SO 4 -CIMS described elsewhere (Eisele and Tanner, 1993;Slusher et al, 2004;Benson et al, 2008;Young et al, 2008). The CDC and octopole ion guide dramatically improve the cleanness of ion mass spectra and the instrument sensitivity ( Fig.…”

Production of N<sub>2</sub>O<sub>5</sub> and ClNO<sub>2</sub> in summer in urban Beijing, China

“…The ambient target molecules were first ionized by reagent ions in the IMR and then detected as adduction products with iodide, for instance ClNO 2 as I · ClNO − 2 at m/z 208 and 210 (I· 37 ClNO − 2 ), and N 2 O 5 as I·N 2 O − 5 at m/z 235 (Slusher et al, 2004;Kercher et al, 2009) at a time resolution of 1 s. Data analysis is performed using the "Tofware" package (version 2.5.11) running in the IGOR Pro (WaveMetrics, OR, USA) environment. The mass axis of UoM-CIMS was calibrated using I − , I − 2 , and I − 3 , while that of IAP-CIMS was calibrated using NO − 3 , I − , I · H 2 O − , I · CH 2 O − 2 , I · HNO − 3 , and I − 3 covering a wide range from m/z 62 to 381.…”

Development of a photochemical source for the production and calibration of acyl peroxynitrate compounds

“…A detailed description of the I − CIMS is presented elsewhere (Slusher et al, 2004). Briefly, APNs are dissociated in a heated inlet, subsequently react with iodide ions (I − ), and are detected as carboxylate anions using a quadrupole mass Figure 1.…”

“…Unless otherwise stated, the inlet dissociator temperature was set to 150 • C for the experiments presented in this work. In response to a well-known dependence of PAN detection on the water concentration in the flow tube (Slusher et al, 2004), a 100 % relative humidity, 10 sccm N 2 flow was added directly to the flow tube. The instrument was tuned to minimize the detection of cluster ions such that the observed I q H 2 O − : I − ratio was 0.002.…”

“…An increasingly popular method is thermal-dissociation chemical ionization mass spectrometry (TD-CIMS) for the measurement of APNs (Slusher et al, 2004;Phillips et al, 2013;Zheng et al, 2011). Comparisons of the TD-CIMS method with other techniques, such as GC and TD-LIF, show reasonably good agreement (Wooldridge et al, 2010;Tyndall et al, 2005).…”