Measurement of HONO, HNCO, and other inorganic acids by negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS): application to biomass burning emissions

Abstract

Abstract. A negative-ion proton-transfer chemical ionization mass spectrometric technique (NI-PT-CIMS), using acetate as the reagent ion, was applied to the measurement of volatile inorganic acids of atmospheric interest: hydrochloric (HCl), nitrous (HONO), nitric (HNO 3 ), and isocyanic (HNCO) acids. Gas phase calibrations through the sampling inlet showed the method to be intrinsically sensitive (6-16 cts/pptv), but prone to inlet effects for HNO 3 and HCl. The ion chemistry was found to be insensitive to water vapor concentrations, in agreement with previous studies of carboxylic acids. The inlet equilibration times for HNCO and HONO were 2 to 4 s, allowing for measurement in biomass burning studies. Several potential interferences in HONO measurements were examined: decomposition of HNO 3 ·NO − 3 clusters within the CIMS, and NO 2 -water production on inlet surfaces, and were quite minor (≤1%, 3.3%, respectively). The detection limits of the method were limited by the instrument backgrounds in the ion source and flow tube, and were estimated to range between 16 and 50 pptv (parts per trillion by volume) for a 1 min average. The comparison of HONO measured by CIMS and by in situ FTIR showed good correlation and agreement to within 17%. The method provided rapid and accurate measurements of HNCO and HONO in controlled biomass burning studies, in which both acids were seen to be important products.

Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

“…Oswald et al (2013) found differences as much as 2 orders of magnitude in HONO emissions from soil samples from different environments (e.g., pH and nutrient contents). In addition, as most of observations in the East Asia regions were conducted with ionchromatography-based methods, more direct HONO quantification techniques such as a chemical ionization mass spectrometry technique (Roberts et al, 2010) need to be used to characterize any potential interferences such a high NO x environment (e.g., N 2 O 5 ). Fig.…”

Nitrous acid formation in a snow-free wintertime polluted rural area

“…Nitric acid (HNO 3 ) was measured by negative-ion protontransfer chemical ionization mass spectrometry (NI-PT-CIMS), with acetate as the reagent ion. This method is described in detail by Roberts et al (2010) and Veres et al (2008). The NI-PT-CIMS was placed on the tower at 10 m a.g.l.…”

A broadband cavity enhanced absorption spectrometer for aircraft measurements of glyoxal, methylglyoxal, nitrous acid, nitrogen dioxide, and water vapor

“…Constant HONO concentrations were generated using a calibration source based on the design by Febo et al (1995) and Roberts et al (2010). Briefly, humidified air mixed with HCl from a permeation tube passes through a sodium nitrite bed (NaNO 2 mixed with glass beads) to generate HONO via acid displacement.…”

“…The wet chemical detection methods are sensitive but generally rely on conversion of HONO to nitrite ion (NO − 2 ) (Appel et al, 1990;Dibb et al, 2002;Kleffmann et al, 2006) and may be susceptible to chemical interferences and sampling artifacts (Stutz et al, 2010). Recently, chemical ionization mass spectrometry with acetate ion (Roberts et al, 2010) or iodide ion chemistry has been successfully used for sensitive HONO detection. Spectroscopic methods for remote sensing include long-path DOAS and MAX-DOAS (Platt et al, 1980;Hendrick et al, 2014).…”