Mapping and quantifying isomer sets of hydrocarbons ( ≥  C<sub>12</sub>) in diesel exhaust, lubricating oil and diesel fuel samples using GC  ×  GC-ToF-MS

Abstract

Abstract. Airborne particles and vapours, like many other environmental samples including water, soils and sediments, contain complex mixtures of hydrocarbons, often deriving from crude oil either before or after fractionation into fuels, lubricants and feedstocks. Comprehensive 2D gas chromatography time-of-flight mass spectrometry (GC × GCToF-MS), offers a very powerful technique that separates and identifies many compounds in complicated hydrocarbon mixtures. However, quantification and identification of individual constituents at high ionization energies would require hundreds of expensive (when available) standards for calibration. Although the precise chemical structure of hydrocarbons does matter for their environmental impact and fate, strong similarities can be expected for compounds having very similar chemical structures and carbon numbers. There is, therefore, a clear benefit in an analytical technique which is specific enough to separate different classes of compounds and to distinguish homologous series while avoiding the need to handle each isomer individually. Varying EI (electron impact) ionization mass spectrometry significantly enhances the identification of individual isomers and homologous compound groups, which we refer to as "isomer sets". Advances are reported in mapping and quantifying isomer sets of hydrocarbons (≥ C 12 ) in diesel fuel, lubricating oil and diesel exhaust emissions. By using this analysis we report mass closures of ca. 90 and 75 % for diesel fuel and lubricating oil, and identify 85 and 75 % of the total ion current for gas-and particulate-phase diesel exhaust emissions.

Insight into the composition of organic compounds ( ≥ C6) in PM2.5 in wintertime in Beijing, China

“…The identified compounds which have no commercial authentic standards were quantified using the calibration curves for similar structure compounds or isomeric compounds. This applicability of quantification of individual compounds using isomers of the same compound functionality (which have authentic standards) has been discussed elsewhere and has a reported uncertainty of 24 % (Alam et al, 2018).…”

“…The branched alkanes, alkyl-benzenes, alkyl-decalins, alkyl-phenanthrene and anthracene (alkyl-Phe and Ant), alkyl-naphthalene (alkyl-Nap), and alkyl-benzaldehyde were identified in the samples with the graphics method of the GC Image version 2.5 (Zoex Corporation, Houston, TX, USA), and the detailed descriptions are given elsewhere (Alam et al, 2018). Briefly, the structurally similar compounds (similar physico-chemical properties) were identified as a group via drawing a polygon around a section of the chromatogram with the polygon selection tool.…”

“…Due to its huge complexity, particulate organic matter is still inadequately characterized up to the present. Hence, the identification of organic compounds in generic groups may be more informative in elucidating the molecular distribution of atmospheric organic compounds and bulk aerosol characteristics (Alam et al, 2018). Previous studies have shown that the organic compounds were highly oxidized during haze days, and secondary formation has made a significant contribution to the particulate matter (PM) (Li et al, 2019).…”

Insight into the Composition of Organic Compounds (≥ C6) in PM2.5 in Wintertime in Beijing, China

“…graphics method of the GC Image v2.5 (Zoex Corporation, Houston, US), and the detailed descriptions are given elsewhere (Alam et al, 2018). Briefly, the structurally similar compounds (similar physicochemical properties) were identified as a group via drawing a polygon around a section of the chromatogram with the polygon selection tool.…”

The influence of particle composition upon the evolution of urban ultrafine diesel particles on the neighbourhood scale

“…Experimental and modelling studies have advanced our understanding of the behaviour of urban air UFPs, e.g. the relevant aerosol dynamics important to the evolution of UFPs in space and time (Jacobson, 2005;Allen et al, 2007;Biswas et al, 2007;Dall'Osto et al, 2011;Nikolova et al, 2011;Karnezi et al, 2014;Karl et al, 2016).…”