A series of smog chamber experiments have been
conducted in which five cyclic monoterpenes were oxidized
by ozone. The evolved secondary aerosol was analyzed
by GC-MS and HPLC-MS for nonvolatile polar oxidation
products with emphasis on the identification of carboxylic
acids. Three classes of compounds were determined at
concentration levels corresponding to low percentage molar
yields: i.e. dicarboxylic acids, oxocarboxylic acids, and
hydroxyketocarboxylic acids. Carboxylic acids are highly
polar and have lower vapor pressures than their corresponding
aldehydes and may thus play an important role in secondary
organic aerosol formation processes. The most abundant
carboxylic acids were the following: cis-pinic acid AB1 (cis-3-carboxy-2,2-dimethylcyclobutylethanoic acid) from α-
and β-pinene; cis-pinonic acid A3 (cis-3-acetyl-2,2-dimethylcyclobutylethanoic acid) and cis-10-hydroxypinonic
acid AB6 (cis-2,2-dimethyl-3-hydroxyacetylcyclobutylethanoic acid) from α-pinene and β-pinene; cis-3-caric
acid C1 (cis-2,2-dimethyl-1,3-cyclopropyldiethanoic acid), cis-3-caronic acid C3 (2,2-dimethyl-3-(2-oxopropyl)cyclopropanylethanoic acid), and cis-10-hydroxy-3-caronic acid C6
(cis-2,2-dimethyl-3-(hydroxy-2-oxopropyl)cyclopropanylethanoic acid) from 3-carene; cis-sabinic acid S1 (cis-2-carboxy-1-isopropylcyclopropylethanoic acid) from sabinene;
limonic acid L1 (3-isopropenylhexanedioic acid), limononic
acid L3 (3-isopropenyl-6-oxo-heptanoic acid), 7-hydroxylimononic acid L6 (3-isopropenyl-7-hydroxy-6-oxoheptanoic
acid), and 7-hydroxylimononic acid L6‘ (7-hydroxy-3-isopropenyl-6-oxoheptanoic acid) from limonene.
The ozonolytic decomposition of terpenes and terpenoids during sampling on Tenax is investigated in an artificial air system at ambient concentration levels. The detrimental effect of 8-150 ppbv ozone depends on the chemical structure of the compounds: saturated terpenoids such as 1,8-cineole, camphor, and bornyl acetate are unaffected by ozone. The terpenes and terpenoids which containing one C-C double bond are slightly decomposed in the order camphene < β-pinene ≈ myrtenal < α-pinene < sabinene ≈ citronellal. The compounds containing two or more double bonds are significantly decomposed in the order d-limonene ≈ citral < linalool < β-ocimene < terpinolene << α-terpinene ≈ β-caryophyllene. For α-pinene, sabinene and d-limonene, their ozonolysis products are found on the tubes: pinonaldehyde, 5-(1-methylethyl)bicyclo[3.1.0]hexan-2-one, and 3-(1-methylethenyl)-6-oxoheptanal. The analytical recoveries are significantly enhanced for many compounds when the sampling duration is reduced from 10 min to 30 s, explained by the time available for ozonolysis. A miniature ozone scrubber with multiple layers of MnO(2)-coated copper nets was developed and thoroughly tested. The optimal number of plies is found to be 8, which ensures quantitative recoveries for all test compounds except α-terpinene, β-caryophyllene, citral, and citronellal. The results that are reported here call into question previous data on terpenes and terpenoids and/or their oxidation products where measurements have been carried out without the prior removal of ozone.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.