Abstract
Abstract. Molecules with hydroperoxide functional groups are of extreme importance to both the atmospheric and biological chemistry fields. In this work, an analytical method is presented for the identification of organic hydroperoxides and peroxy acids (ROOH) by direct infusion of liquid samples into a positive-ion atmospheric pressure chemical ionization–tandem mass spectrometer ((+)-APCI-MS/MS). Under collisional dissociation conditions, a characteristic neutral loss of 51 Da (arising from loss of H2O2+NH3) from ammonium adducts of the molecular ions ([M + NH4]+) is observed for ROOH standards (i.e. cumene hydroperoxide, isoprene-4-hydroxy-3-hydroperoxide (ISOPOOH), tert-butyl hydroperoxide, 2-butanone peroxide and peracetic acid), as well as the ROOH formed from the reactions of H2O2 with aldehydes (i.e. acetaldehyde, hexanal, glyoxal and methylglyoxal). This new ROOH detection method was applied to methanol extracts of secondary organic aerosol (SOA) material generated from ozonolysis of α-pinene, indicating a number of ROOH molecules in the SOA material. While the full-scan mass spectrum of SOA demonstrates the presence of monomers (m∕z = 80–250), dimers (m∕z = 250–450) and trimers (m∕z = 450–600), the neutral loss scan shows that the ROOH products all have masses less than 300 Da, indicating that ROOH molecules may not contribute significantly to the SOA oligomeric content. We anticipate this method could also be applied to biological systems with considerable value.
Highlights
Organic hydroperoxides and peroxy acids (ROOH) are produced by the gas-phase oxidation of volatile organic compounds (VOCs) (Jackson et al, 1999; Lee et al, 2000; Atkinson and Arey, 2003), as well as in cloud and wet aerosols (Zhao et al, 2013; Lim and Turpin, 2015)
Note that we do not attempt to interpret the mass spectra of ROOH and other standards obtained under full-scan and selected ion monitoring (SIM) modes due to the presence of stabilizers and other impurities in the standard samples that make the mass spectra complex
Organic hydroperoxides are molecules of crucial importance to atmospheric chemistry, arising under VOC oxidation schemes that proceed under low-NOx conditions
Summary
Organic hydroperoxides and peroxy acids (ROOH) are produced by the gas-phase oxidation of volatile organic compounds (VOCs) (Jackson et al, 1999; Lee et al, 2000; Atkinson and Arey, 2003), as well as in cloud and wet aerosols (Zhao et al, 2013; Lim and Turpin, 2015). Atmospheric oxidation of VOCs leads to secondary organic aerosol (SOA), an important fraction of the atmospheric aerosol burden. Both modeling and experimental studies indicate that organic peroxides (i.e. organic peroxides (ROOR) and ROOH species) are major components of SOA (Jenkin, 2004; Bonn et al, 2004; Docherty et al, 2005). Classified as one component of reactive oxygen species (ROS), ROOH are hazardous, irritating to skin, eyes and mucous membranes. They cause progressive oxidative damage, cell death and even cancer (Liou and Storz, 2010)
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