NSO-compounds in oil-bearing fluid inclusions revealed by FT-ICR-MS in APPI (+) and ESI (-) modes: A new method development

The origins of hydrocarbons occurring in oil-bearing fluid inclusions (FIs) have been studied in detail over the last four decades, but very little is known about co-occurring nitrogen, sulfur and oxygen (NSO)-containing compounds. Here, we outline a new method for gathering valuable information on NSO-compounds using the Fourier Transform-Ion Cyclotron Resonance-Mass Spectrometry (FT-ICR-MS) in combination with Atmospheric Pressure Photoionization in positive ion mode (APPI (+)) and Electrospray Ionization in negative ion mode (ESI (-)). A key element was to develop a rigorous acid-free cleaning protocol to make oil inclusions from a broad range of host materials accessible to the very sensitive FT-ICR-MS technique. Although oil contamination from surrounding organic matter could not be entirely eliminated, the procedure enables distinction of external contaminants and identification of affected NSO-compound classes allowing a conditional interpretation of the FT-results of FL samples, especially for compounds measured in the APPI (+) mode. First insights into the high molecular weight hydrocarbons and NSO-compounds in FL oils are presented here using examples from Germany, Tunisia, Pakistan and Mexico. (C) 2020 Elsevier Ltd. All rights reserved.