title: Analysis of α-acyloxyhydroperoxy aldehydes with electrospray ionization-tandem mass spectrometry (ESI-MS(n)).
abstract: A series of α-acyloxyhydroperoxy aldehydes was analyzed with direct infusion electrospray ionization tandem mass spectrometry (ESI/MS(n)) as well as liquid chromatography coupled with the mass spectrometry (LC/MS). Standards of α-acyloxyhydroperoxy aldehydes were prepared by liquid-phase ozonolysis of cyclohexene in the presence of carboxylic acids. Stabilized Criegee intermediate (SCI), a by-product of the ozone attack on the cyclohexene double bond, reacted with the selected carboxylic acids (SCI scavengers) leading to the formation of α-acyloxyhydroperoxy aldehydes. Ionization conditions were optimized. [M + H](+) ions were not formed in ESI; consequently, α-acyloxyhydroperoxy aldehydes were identified as their ammonia adducts for the first time. On the other hand, atmospheric-pressure chemical ionization has led to decomposition of the compounds of interest. Analysis of the mass spectra (MS(2) and MS(3)) of the [M + NH(4)](+) ions allowed recognizing the fragmentation pathways, common for all of the compounds under study. In order to get detailed insights into the fragmentation mechanism, a number of isotopically labeled analogs were also studied. To confirm that the fragmentation mechanism allows predicting the mass spectrum of different α-acyloxyhydroperoxy aldehydes, ozonolysis of α-pinene, a very important secondary organic aerosol precursor, was carried out. Spectra of the two ammonium cationized α-acyloxyhydroperoxy aldehydes prepared with α-pinene, cis-pinonic acid as well as pinic acid were predicted very accurately. Possible applications of the method developed for the analysis of α-acyloxyhydroperoxy aldehydes in SOA samples, as well as other compounds containing hydroperoxide moiety are discussed.
authors.affiliation: Faculty of Chemistry, University of Warsaw, al. Żwirki i Wigury 101, 02-089, Warsaw, Poland.
authors.forename: Bartłomiej
authors.initials: B
authors.lastname: Witkowski
authors.forename: Tomasz
authors.initials: T
authors.lastname: Gierczak
mesh_terms: D000447:Aldehydes / Q000032:analysis / Q000737:chemistry*; D000081008:Bicyclic Monoterpenes; D002264:Carboxylic Acids / Q000737:chemistry; D053138:Cyclohexenes / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry*; D039821:Monoterpenes / Q000737:chemistry; D010126:Ozone / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D000447:Aldehydes; D000081008:Bicyclic Monoterpenes; D002264:Carboxylic Acids; D053138:Cyclohexenes; D039821:Monoterpenes; C052568:cyclohexene; D010126:Ozone; D006861:Hydrogen Peroxide; C005451:alpha-pinene