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Rationale The volatile compounds generated by the electrochemical reduction of atmospheric carbon dioxide and nitrogen include isobaric methanol (CH3OH) and, potentially, hydrazine (N2H4). To achieve quantification of hydrazine molecules by selected ion flow tube mass spectrometry (SIFT‐MS), its reactions with H3O+, NO+ and O2+ reagent ions must be understood. Methods A SIFT study (using a SIFT‐MS instrument) was carried out to obtain rate coefficients and product ions for the reactions of H3O+, NO+ and O2+ reagent ions with N2H4 and CH3OH molecules present in the humid headspace of their aqueous solutions. Using the kinetics data obtained, solution headspace concentrations were determined for both compounds as a function of their liquid‐phase concentrations at 10, 20 and 35°C. Results Both compounds react with H3O+ ions via rapid proton transfer to produce CH3OH2+ and H5N2+ ions with the common m/z value of 33. It is revealed that NO+ rapidly transfers charge to N2H4 (rate coefficient k = 2.3 × 10−9 cm³ s−1) but only slowly associates with CH3OH (k2eff = 7.1 × 10−11 cm³ s−1). Thus, selective analysis can be achieved using both H3O+ and NO+ reagent ions. The headspace methanol vapour concentration was found to increase with increasing solution temperature, but that of hydrazine decreased with an associated increase of ammonia (NH3) as measured with O2+ reagent ions. Conclusions The isobaric compounds methanol and hydrazine can be separately analysed in real time by SIFT‐MS using H3O+ and NO+ reagent ions, even when they co‐occur in humid air. The evolution of hydrazine from aqueous solutions can be quantitatively monitored together with its decomposition at elevated temperatures. [ABSTRACT FROM AUTHOR]

Rationale Nitrogen oxides or NOx (NOx = NO + NO2) play an important role in air quality, atmospheric chemistry, and climate. The isotopic compositions of anthropogenic and natural NO2 sources are wide-ranging, and they can be used to constrain sources of ambient NO2 and associated atmospheric deposition of nitrogen compounds. While passive sample collection of NO2 isotopes has been used in field studies to determine NOx source influences on atmospheric deposition, this approach has not been evaluated for accuracy or precision under different environmental conditions. Methods The efficacy of NO2 passive sampler collection for NO2 isotopes was evaluated under varied temperature and relative humidity (RH) conditions in a dynamic flux chamber. The precision and accuracy of the filter NO2 collection as nitrite (NO2-) for isotopic analysis were determined using a reference NO2 gas tank and through inter-calibration with a modified EPA Method 7. The bacterial denitrifer method was used to convert 20 μM of collected NO2- or nitrate (NO3-) into N2O and was carried out on an Isoprime continuous flow isotope ratio mass spectrometer. Results δ15N-NO2 values determined from passive NO2 collection, in conditions of 11-34 °C, 1-78% RH, have an overall accuracy and precision of ±2.1 ‰, and individual run precision of ±0.6 ‰. δ18O-NO2 values obtained from passive NO2 sampler collection, under the same conditions, have an overall precision of ± 1.3 ‰. Conclusions Suitable conditions for passive sampler collection of NO2 isotopes are in environments ranging from 11 to 34 °C and 1 to 78% RH. The passive NO2 isotope measurement technique provides an accurate method to determine variations in atmospheric δ15N-NO2 values and a precise method for determining atmospheric δ18O-NO2 values. The ability to measure NO2 isotopes over spatial gradients at the same temporal resolution provides a unique perspective on the extent and seasonality of fluctuations in atmospheric NO2 isotopic compositions. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]