Hyphenation of thermal analysis to ultra-high resolution Mass Spectrometry (FT-ICR MS) using Atmospheric Pressure Chemical Ionization (APCI) for studying composition and thermal degradation of complex materials.
In this study, the hyphenation of a thermobalance to an ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometer (UHR FT-ICR MS) is presented. Atmospheric pressure chemical ionization (APCI) is used for efficient ionization. The evolved gas analysis (EGA), using high resolution mass spectrometry allows the time-resolved molecular characterization of thermally induced processes in complex materials or mixtures, such as biomass or crude oil. The most crucial part of the setup is the hyphenation between the thermobalance and the APCI source. Evolved gases are forced to enter the atmospheric pressure ionization interface of the MS by applying a slightly over-pressure at the thermobalance side of the hyphenation. Using the FT-ICR exact mass data, detailed chemical information is gained by calculation of elemental compositions from the organic species, enabling a time and temperature resolved, highly selective detection of the evolved species. An additional selectivity is gained by the APCI ionization, which is particularly sensitive towards polar compounds. This selectivity on the one hand misses bulk components of petroleum samples such as alkanes and does not deliver a comprehensive view, but on the other hand focuses particularly on typical evolved components from biomass samples. As proof of principle the thermal behavior of different fossil fuels: heavy fuel oil, light fuel oil and a crude oil, and different lignocellulosic biomass, namely beech, birch, spruce, ash, oak and pine as well as commercial available softwood and birch-bark pellets were investigated. The results clearly show the capability to distinguish between certain wood types through their molecular patterns and compound classes. Additionally, typical literature known pyrolysis biomass marker were confirmed by their elemental composition, such as coniferyl aldehyde (C10H10O3), sinapyl aldehyde (C11H12O4), retene (C18H18), and abietic acid (C20H30O2).