Lindsay P. Brown, Wesley B. Seaton, Joshua B. Powers, Shawn R. Campagna
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引用次数: 0
Abstract
Atmospheric pressure chemical ionization (APCI) is often used in the analysis of linear saturated hydrocarbons (LSHs) as this ionization technique commonly produces [M − H]+ ions in high abundance. However, APCI (along with other atmospheric pressure sources) is often impacted by in-source oxidation, leading to a variety of ionic products. Identifying these products and understanding their mechanisms of formation is crucial for characterizing complex mixtures with substantial hydrocarbon content, such as those found in the petrochemical industry. In this study, in-source oxidation of LSHs was observed in gas chromatography (GC) coupled to high-resolution mass spectrometry (HRMS) via a custom-built APCI interface. Studies showed that the abundance of these oxidized ions correlated positively with atmospheric water, yet occurred without the inclusion of water-based oxygen as judged by experiments with stable isotope-labeled water. The oxidation of LSHs was further influenced by the reactive species in the ionization atmosphere. Fragmentation data using stable isotope-labeled LSH standards unveiled multiple structurally unique ions with one or more oxidation sites on both primary and secondary carbons. These ionic products bear resemblance to combustion byproducts, suggesting the instrumental configuration fosters plasma-assisted combustion-like processes that encourage the radical-mediated oxidation of LSHs rather than generate [M − H]+. Through these investigative efforts, a mechanism analogous to combustion was proposed for the formation of LSH oxidation products in GC-APCI-HRMS. Data demonstrate that these ions are robustly generated in petrochemical products, allowing for proper characterization of these complex mixtures.
期刊介绍:
The Journal of Mass Spectrometry publishes papers on a broad range of topics of interest to scientists working in both fundamental and applied areas involving the study of gaseous ions.
The aim of JMS is to serve the scientific community with information provided and arranged to help senior investigators to better stay abreast of new discoveries and studies in their own field, to make them aware of events and developments in associated fields, and to provide students and newcomers the basic tools with which to learn fundamental and applied aspects of mass spectrometry.