Comprehenisve two-dimensional liquid chromatography coupled to mass spectrometry for quali-quantitative analysis of bio-oils aqueous phases from different biomasses

Abstract

Agrifood by-products are perfect candidates to be further processed under the concept of circular economy, in order to increase their added value. A strategy to valorize agrifoodrelated by-products is based on pyrolysis processes. Pyrolysis is based on the application of high temperatures, typically around 500 ºC in the absence of oxygen to produce the thermal decomposition of a particular biomass. The result of this process is a liquid product termed bio-oil which is composed of an organic phase and an aqueous phase. The aqueous phase is characterized by many compounds such as ketones, alcohols, benzenediols, nitrogen compounds. Due to the complexity of these samples, the use of comprehensive two-dimensional liquid chromatography (LC×LC) where two columns of different selectivity are coupled by means of a switching valve is very interesting. In this contribution, eight different bio-oils were characterized by LC×LC employing reversed phase separations in both dimensions. Namely, an amide column (150x2.1 mm I.D, 3.5m dp) and a C18 silica column (50x4.6 mm, 2.7 m dp) were used in the first (1D) and second (2D) dimension, respectively. Twenty-two compounds were identified and quantified with good LODs (limit of detection) and LOQs (limit of quantification). Peak capacity values and orthogonality degrees were also calculated and compared. In order to investigate similarities and differences among the bio-oil samples, multivariate analysis, specifically PCA, was performed. The use of PCA enabled us to discriminate bio-oil into different groups, which showed distinct quali-quantitative compositions.