Ion mobility mass spectrometry of in situ generated biomass pyrolysis products

Lignocellulosic biomass is an abundant and renewable energy source that can be used as biofuel after physicochemical conversion, e.g. by fast pyrolysis. However, the chemical variations from wood and other biomass species affect this conversion. Chemical characterization is needed to obtain more information on the pyrolysis products depending on the biomass type and pyrolysis conditions. Here, we compared the fast pyrolysis molecular pattern of five lignocellulosic biomasses (beech, hickory, miscanthus and two brands of resinous wood pellets) obtained from a direct analysis method of solid samples coupled to ion mobility and time of flight mass spectrometry (IM-TOF MS). Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) with its ultra-high resolving power was used, with a similar solid analysis introduction approach, to probe for the presence of possible unresolved isobaric compounds in the IM-TOF MS analysis. Isobaric interferences were found to be negligible and molecular formulas determined using IM-TOF MS were confirmed as reliable. Principal component analysis on the molecular formulas allowed the extraction of marker ions preferentially found in hardwood and miscanthus or softwood species. Ion mobility drift time values from these biomass markers were converted into collision-cross sections (CCS), a direct measure of structure and shape of a molecule. No significant CCS differences were observed between the markers of the five wood samples, showing isomeric similarities between the samples. In order to move forward on the structural elucidation and characterization of the pyrolysis products, IM-TOF MS and tandem mass spectrometry (MS/MS) were performed on standard molecules and compared to the biomass pyrolysis products, highlighting the presence of isomers in the wood pyrolysis products.