Characterization of Alkane Oxidation Products in a Corona-Discharge Reactor Using Ammonia-Doped Ion Mobility–Mass Spectrometry

This study examines the oxidation of C 5 –C 8 alkanes in an external corona-discharge reactor. Oxidation products were characterized using ion mobility spectrometry (IMS) and tandem IMS–mass spectrometry (IMS-MS) with an internal corona-discharge APCI source. This configuration enables structural isomer resolution and provides deeper insight into the molecular composition of the oxidation products. IMS-MS analysis showed that alkane (M) oxidation produces mainly ketones ([M+O–2H]) and diketones ([M+2O–4H]), with 3-ketone isomers dominating. Under standard APCI conditions, H + (H 2 O) n reactant ions protonated these products, generating complex IMS spectra for [M+O-2H].H + and [M+2O-4H].H + . Introducing NH 3 as a dopant shifted the primary reactant ion to NH 4 + (H 2 O) n, forming [M+O–2H]. NH 4 + and [M+2O–4H].NH 4 + adducts with similar collision cross sections. This simplified the IMS spectra to a single peak, enhanced sensitivity, and improved suitability for analytical applications. Using this approach, quantitative analysis of selected alkanes yielded detection limits of 0.01–0.1 ppm v .