Research Projects

Project at a Glance

Title: Identities and behavior of multi-functional carbonyls in simulated and ambient atmospheric environments.

Principal Investigator / Author(s): M. Judith Charles

Contractor: UC Davis

Contract Number: 96-303


Research Program Area: Atmospheric Processes

Topic Areas: Chemistry & Reactivity, Monitoring


Abstract:

We developed and tested a field method to measure carbonyls and multifunctional carbonyls in air. The method involves sampling air using impingers filled with an aqueous solution of O-(2,3,4,5,6-pentafluorobenzyl) -hydroxylamine (PFBHA) to derivatize carbonyls in situ. After extraction of the derivatives from water, an aliquot of the extract is reacted with bis(trimethylsilyl) trifluoroacetamide (BSTFA) to silylate the hydroxyl group on hydroxy carbonyls and oxo acids. The PFBHA derivatives of aldehydes, ketones, and dicarbonyls and the PFBHA / BSTFA of hydroxy carbonyls and oxo acids were detected by using gas chromatography along with electron-impact ionization (EI), methane chemical ionization (CI) and pentafluorobenzyl alcohol chemical ionization (PFBOH CI) ion trap mass spectrometry. We identified methyl vinyl ketone, methacrolein, methyl glyoxal, glycolaldehyde and hydroxy acetone in Azusa, California and methacrolein, methyl vinyl ketone, 3-hydroxy-2-butanone, and hydroxy acetone in Davis, California air. We also identified 2,3-butanedione and glyoxal in Davis air. However, since the concentration of these compounds was greater in samples collected without removing ozone from the airstream, they may be artifacts generated from the oxidation of other species. We report concentration ranges of 245 to 348 pptv for methyl vinyl ketone, 113 to 232 pptv for methacrolein, ND (non-detectable) to 182 pptv for methyl glyoxal, ND to 840 pptv for glycolaldehyde and ND to 534 pptv for hydroxy acetone in Azusa air. To our knowledge, this is the first report of 3-hydroxy-2-butanone and hydroxy acetone in the ambient atmospheric environment. PFBOH chemical ionization was critical to identify glycolaldeyde and hydroxy acetone in the presence of co-eluting interferences, and to confirm the identity of glyoxal. By extrapolation, the method detection limit at a S:N of 3:1 is 1 pptv for methyl vinyl ketone, 3 pptv for methacrolein, 12 pptv for methyl glyoxal, 11 pptv for glycolaldehyde and 49 pptv for hydroxy acetone. Although, herein we only report the measurement of select carbonyls, an advantages of the method as demonstrated in chamber studies, is that the method is suitable for the measurement of a broad range of carbonyls, including aldehydes, ketones, hydroxy carbonyls, epoxy carbonyls and oxo acids. In addition, the method enables the determination of molecular weights of carbonyls for which authentic standards do not exist.


 

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