The goal of this paper is the evaluation of fast two‐dimensional gas chromatography applied to bio‐oil samples. Bio‐oils are complex matrixes that usually are analyzed by conventional gas chromatography, involving long columns, long time of analysis due to slow heating rates, and consequently, high cost associated to time consumed. Fast gas chromatography techniques are based on the use of narrow capillary columns that allow the achievement high‐speed separations for complex samples, maintaining excellent resolution. Firstly, the two‐dimensional gas chromatography method was optimized varying the heating rate (10, 15 and 20°C min−1) and achieving the optimal separation at 15°C min−1. This method allies a good separation of bio‐oil constituents with shorter time analysis. The developed method and the traditional conventional two‐dimensional gas chromatography method (used in previous studies) were applied in the analysis of a mixture of 30 standard compounds. Despite coelutions of short retention time peaks (compounds with very similar physical‐chemical properties), the fast two‐dimensional gas chromatography method showed an increase in chromatographic signal and a noise reduction. Good results were also obtained in the real bio‐oil sample. Fast two‐dimensional gas chromatography maintained all the chromatographic information from conventional two‐dimensional gas chromatography, reducing drastically the total time of analysis.
Green coconut (Cocos nucifera L. var. dwarf) is one of the most cultivated commodities on the Brazilian coast. Most green coconut waste is burned or disposed of as garbage on coconut-producing properties, on the streets of large cities, and in landfills. Incorrect disposal of coconut waste causes several problems as proliferation of disease vectors, occupation of large areas in landfills, production of gases, and contamination of soil and groundwater. The conversion of this biomass can be carried out through pyrolysis. The bio-oil from the pyrolytic process has a complex chromatographic profile requiring a fractionation step to improve its separation and characterization. In this work, the bio-oil was fractionated according to its acidity (strongly acidic, slightly acidic, basic, and neutral), and both the bio-oil and the fractions were analyzed by fast-GC × GC/TOFMS. The fractionation process used was able to reduce the complexity of the generated crude bio-oil. Three hundred and five different compounds were identified between the fractions analyzed and the crude bio-oil. The time for each analysis was 19 min, demonstrating the gain of the separation/detection technique without losing quality in the identification. The majority of the compounds in the fractions were phenol, catechols, eugenols, and furfural, reinforcing the idea of using this bio-oil as a precursor in the chemical industry.
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.
This study presents and discusses the state of the art of Two-Dimensional Comprehensive Gas Chromatography (GC×GC) developed in Brazil. GC×GC has been the focus of studies in Brazil since 2009, based on successful experiences in cooperation with researchers from Australia and Italy. The result of these researches led to the installation of many laboratories in Brazilian Universities and Research Centers, similar to others in foreign countries and the development of research, mostly involving applications of the technique to Brazilian matrices. In this review we present applications of GC×GC involving the pyrolysis of Brazilian agroindustrial residues, such as cane straw, sawdust, coconut fiber, fruit seeds, rice husks, spent coffee grounds, among others. The most used detection techniques for GC×GC have been mass spectrometry with fast quadrupole analyzer (GC×GC/qMS) and time of flight (GC×GC/TOFMS). These studies showed the possibility of identifying many organic compounds in the bio-oils produced, especially oxygenated ones such as phenols, ketones, acids and esters. Several studies suggest catalytic pyrolysis as a way to generate less oxygen-compounds directing the application of this bio-oil to the area of biofuels. However, the compounds found and their relative concentration, indicates that the best uses should be associated with the processing industry such as pharmaceuticals, chemicals, polymers and food.
DOI: https://doi.org/10.1002/elps.201800129 The cover picture shows that the bio‐oil study of coconut fiber pyrolysis ‐ the largest constituent of urban waste in the Brazilian Northeast beaches ‐ through fast GC‐GC/TOFMS indicated a significant reduction in analysis time without loss of resolution and increased detectability. This result allows the analysis of several samples in a short time, appropriate for the statistical treatment of the data, essential for the reliability of the results, definition of the environmental impacts and indication of suitable uses for the pyrolysis products.
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