The speciation of the organic compounds of slow pyrolysis bio-oils from Brazilian tropical seed cake fruits using high-resolution techniques: GC × GC-TOFMS and ESI(±)-Orbitrap HRMS

Abstract

In view of increasing energy needs in modern society and the desire to replace current energy sources with clean and sustainable ones, biomass is now considered to be a renewable energy source with considerable potential. As Brazil is a major agricultural producer, the reuse of its agroindustrial residues is being explored to find ways to utilize this waste. In the current study, soursop seed cake (SSC) and bocaiuva seed cake (BSC) were processed using slow pyrolysis to obtain bio-oil. Comprehensive two-dimensional gas chromatography (GC × GC) with time-of-flight (TOF) mass spectrometry (MS) (GC × GC-TOFMS), and positive ion and negative ion (±) electrospray ionization (ESI), coupled with Orbitrap high-resolution (HR) mass spectrometry (MS) (HRMS) (i.e., ESI(±)-Orbitrap HRMS), was performed to provide complementary and comprehensive characterization of the bio-oils, without pre-treatment. As a result, 414 and 222 analytes were tentatively identified in the SSC and BSC bio-oils, respectively. The tentatively identified compound classes were acids, esters, ketones, phenols, cyclopentanones, furanes, diols, amides, pyridines, pyrroles, and hydrocarbons. Compounds with molecular weights in the range of m/z 100–300 were detected in the bio-oils using ESI(±)-Orbitrap HRMS. The N2 class was the most abundant in positive ion mode, representing 37% and 48% of relative abundance in the SSC and the BSC bio-oils, respectively. These data support the data obtained using GC × GC-TOFMS. The O2 heteroatom class was the most abundant for both types of bio-oil in negative ion mode, which were assigned to the carboxylic acid class previously identified by GC × GC-TOFMS. Lauric, palmitic, and oleic acids were found to be in high abundance, similar to the results achieved using GC × GC-TOFMS.