Application of orbitrap mass spectrometry for analysis of model bio-oil compounds and fast pyrolysis bio-oils from different biomass sources

Pyrolysis bio-oils have great potential for the future use as biofuels and source of oxygenated chemicals. To optimize a pyrolysis process, detailed knowledge about the chemical composition of bio-oils is necessary. In recent years, high-resolution mass spectrometry (HRMS) has successfully been used to the characterization of pyrolysis bio-oils from lignocellulosic biomass. This method enabled to detect thousands of semivolatile and nonvolatile, high-molecular-weight bio-oil compounds and provided partial information about their structure. In this work, we used high-resolution orbitrap mass spectrometry to characterize semivolatile and nonvolatile, high-molecular-weight compounds of four bio-oils obtained from the ablative flash pyrolysis of different biomass sources. Before the analyses of these bio-oils, we analyzed model bio-oil compounds and commercially available bio-oil from fast pyrolysis of wood using positive-ion and negative-ion electrospray (ESI) and positive-ion and negative-ion atmospheric pressure chemical ionization (APCI) orbitrap mass spectrometry and compared the results. Based on this comparison, a combination of negative-ion ESI and APCI was found to be well suited for the characterization of pyrolysis bio-oils; these techniques were thus used for the study of bio-oils from different biomass sources and the obtained results were compared. In the studied bio-oils, mostly compounds with 1-8 oxygen atoms per molecule were detected and their degree of unsaturation (DBE) was about 1-10 (negative-ion ESI) and 1-17 (negative-ion APCI), respectively. Among the studied bio-oils, the differences were observed mostly in abundances of their major compounds (compound classes). The analyses of model bio-oil compounds brought valuable information about their behavior during the HRMS characterization of bio-oils. The presented results could help to improve the understanding of bio-oil composition and HRMS characterization of bio-oils and facilitate their further utilization.