Preparation, Analysis, and Atmospheric Production of Multifunctional Organic Nitrates

Ambient measurements of multifunctional organic nitrates have become necessary to understand the complete tropospheric NO_y budget. Laboratory studies indicate that multifunctional organic nitrates that are produced from OH and NO₃ reaction with alkenes may be important; however, they have yet to be detected in atmospheric samples. We have synthesized several C₃−C₆ alkyl nitrates, α,β-hydroxynitrates, and dinitrates that are produced from oxidation of atmospheric hydrocarbons. In this paper we report on procedures for their synthesis and purification, and on results of structural characterization by ¹H NMR and mass spectrometry. All organic nitrates were found to be stable on charcoal adsorbent (often used for sampling) for periods of weeks. Although good chromatographic separation is possible, we find that there may be serious problems with irreversible adsorption on column or injection port surfaces that may interfere with quantitative measurement. However, when the columns are properly conditioned, reproducible analyses can be conducted. We report the relative ECD response for all compounds for different injection systems. We have determined the yield of 2-nitrooxy-3-hydroxybutane formation from OH reaction with cis-2-butene (in the presence of NO) to be 0.037 ± 0.009. The possible causes, including column conditioning, of the elusive nature of the hydroxynitrates and dinitrates in GC/ECD chromatographic analyses of ambient air samples are discussed.