THESIS
2022
1 online resource (xiv, 85 pages) : illustrations (some color)
Abstract
Nitro polycyclic aromatic hydrocarbons (nPAHs) are a family of highly toxic and carcinogenic
compounds which are dispersed into the atmosphere. Due to these properties, nPAHs are a
concern for public health and thus have been the focus of many research papers over the
past two decades. nPAHs can be produced through primary and secondary formation via a
multitude of sources. It is important, therefore, to observe these compounds by identifying
the sources from ambient air samples. In this thesis work, nPAHs from two different sites
were quantified using a method coupling thermal-desorption (TD) for sample introduction
and gas chromatography-mass spectrometry (GC-MS) for separation and detection.
In this method the use of TD greatly reduced sample preparation, whilst, negative chemical
io...[
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Nitro polycyclic aromatic hydrocarbons (nPAHs) are a family of highly toxic and carcinogenic
compounds which are dispersed into the atmosphere. Due to these properties, nPAHs are a
concern for public health and thus have been the focus of many research papers over the
past two decades. nPAHs can be produced through primary and secondary formation via a
multitude of sources. It is important, therefore, to observe these compounds by identifying
the sources from ambient air samples. In this thesis work, nPAHs from two different sites
were quantified using a method coupling thermal-desorption (TD) for sample introduction
and gas chromatography-mass spectrometry (GC-MS) for separation and detection.
In this method the use of TD greatly reduced sample preparation, whilst, negative chemical
ionization (NCI) mass spectrometry provides sensitive detection. GC-MS is an analytical
instrument that has many different approaches, this includes TD and NCI which can be
regarded as components of the method. The combination of these forms the TD-GC-NCI-MS.
This method was used to quantify 7 common nPAHs within 60 PM
2.5 collected from
Tsuen Wan (TW) in Hong Kong and 10 PM
2.5 samples collected from Beijing (BJ). The
concentration of these nPAHs ranged from below the detection limits to 28.4 pg/m
3. With 9-nitroathracene and 4-nitropyrene being the most common nPAHs within the samples. The source apportionment results, as well as correlation matrices showed that TW is likely to be
influenced by biomass burning.
The physiochemical property LogK
OA was used to predict the relative retention time of 11
other common nPAHs within 10 PM
2.5 collected from TW. The octanol-air partitioning
coefficient (K
OA) is the concentration of the compound that is in 1-octanol divided by the
concentration of the compound in that is the air. Two common product ions, the molecular
ion (M) and the molecular ion +1 (M+1) were used to preliminary identify if the peaks at
these relative retention times were the 11 common nPAHs. 64.5% of these peaks contained
M but only 15.5% also contained the M+1.
Further research into the identification of nPAHs without the use of a large number of
standards is suggested.
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