Analyzes of hydrocarbons by atmosphere pressure chemical ionization FT-ICR mass spectrometry using isooctane as ionizing reagent

The analysis of hydrocarbon using atmospheric or ambient ionization techniques still remains a challenge in mass spectrometry. Traditionally, the ionization occurs via protonation or deprotonation and thus the molecules of interest must have a basic or acidic group to generated [M+H]+ or [M−H]− ions. To overcome such limitation, it is proposed a simple, easy, fast and powerful analytical methodology to ionize saturated (linear and branched), unsaturated, and cyclic hydrocarbons as well as polyaromatic hydrocarbons by atmospheric pressure chemical ionization (APCI) using small hydrocarbons as reagents in a FT-ICR mass spectrometer. These molecules may be present in hydrocarbon fraction samples and paraffin/crude oil blends. Among the APCI hydrocarbon reagents, isooctane provided the best results when compared to pentane, hexane, cyclohexane and heptane. The method renders the ionization of hydrocarbons to yield [M−H]+ ions with no associated fragmentation using nitrogen as sheath gas.