LC-MS analysis of aerosol particles from the oxidation of α-pinene by ozone and OH-radicals
Other literature type
Larsen, B. R.
Jensen, N. R.
(issn: 1680-7324, eissn: 1680-7324)
The time resolved chemical composition of aerosol particles, formed by the oxidation of
alpha-pinene has been investigated by liquid chromatography/mass spectrometry (LC-MS) using
negative and positive ionisation methods (ESI(-) and APCI(+)). The experiments were
performed at the EUPHORE facility in Valencia (Spain) under various experimental
conditions, including dark ozone reactions, photosmog experiments with low
NO<sub>x</sub> mixing ratios and reaction with OH radicals in the absence of
NO<sub>x</sub> (H<sub>2</sub>O<sub>2</sub>-photolysis). Particles were sampled on PTFE f
ilters at different stages of the reaction and extracted with methanol. The
predominant products from alpha-pinene in the particulate phase are cis-pinic acid, cis-pinonic
acid and hydroxy-pinonic acid isomers. Another major compound with molecular weight 172
was detected, possibly a hydroxy-carboxylic acid. These major compounds account for
50% to 80% of the identified aerosol products, depending on the time of sampling and type of
experiment. In addition, more than 20 different products have been detected and structures
have been tentatively assigned based on their molecular weight and responses to the different
ionisation modes. The different experiments performed showed that the aerosol formation is
mainly caused by the ozonolysis reaction. The highest aerosol yields were observed in the
dark ozone experiments, for which also the highest ratios of mass of identified products to the
formed aerosol mass were found (30% to 50%, assuming a density of 1 g cm<sup>-3</sup>).