Chromatographic analysis of N-compounds from the pyrolysis of spent coffee grounds

Coffee is an important agricultural product grown worldwide and one of the most consumed beverages in the world. However, its consumption produces a large amount of waste that can be used in industry, benefiting the environment. Thus, the objective of this work was to pyrolyze spent coffee ground generated through the extraction of the coffee beverage (hot aqueous extraction) using two types of coffee, the traditional and the decaffeinated one, and subsequently apply the acid-base-neutral extraction technique to produce bio-oils. This approach aims to isolate nitrogenous compounds, based on the industrial and pharmacological importance of this class of compounds. The acid-base-neutral extraction technique used is simple, of low cost, and aims to pre-concentrate the nitrogenous compounds based on the basic character given by the nitrogen present in these molecules. The analysis of crude bio-oils (before the fractionation) and the respective fractions was performed by gas chromatography-Quadrupole-mass spectrometry. The bio-oils showed high levels of fatty acids, hydrocarbons, and other oxygen compounds, with only traces of nitrogenated compounds being identified. The acid-base-neutral extraction, after solvent recovery, allowed pre-concentration of these compounds and their identification, highlighting quinolines among the most important compounds and with the greatest biotechnological application.