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14 декабря, 2021
The most widely used analytical technologies for bioenergy chains are described
below:
• Titrimetry or volumetry determination of ions, especially by means of compl- exation reactions, neutralization or oxidation-reduction, resulting in the color change of the solution; this is the case of cation determination for feedstock and biofuels quality control (Artiga et al. 2005);
• Gravimetry determination of ions through complexation reactions, redox and precipitation, by means of drying and weighing the compound formed/ solid; this is the case of anion determination in effluent. For suspended solids, it proceeds only to water evaporation and subsequent weighing of the solid
obtained. Gravimetry can be applied for feedstock and biofuels quality control (Seixo et al. 2004);
• Thermal analysis determining the water content and ash, loss of mass for constituents versus temperature, thermal stability, among other parameters associated with temperature effects on the material: thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC)—can be applied for processes, feedstock, and biofuels quality control (Kanaujia et al. 2013);
• Electrochemical the determination of metal oxidation states, quantification of organic and inorganic compounds, polar contaminants in effluents or products: potentiometry, voltammetry, polarography, and amperometry—can be applied for quality control of biofuels (Takeuchi 2007);
• Chromatography (liquid and gas) identification and quantification of organic compounds (volatile, semi-volatile, and nonvolatile) and inorganic, polar, and nonpolar, such as sugars from sugarcane or starch, and its products of conversion processes: high performance liquid chromatography (HPLC) or ultra-high performance liquid chromatography (UPLC) with refractive index, ultraviolet-visible, diode array, fluorescence, mass spectrometry, and light scattering detectors; gas chromatography (CG) with flame ionization, thermal conductivity, electron conductivity, and mass spectrometry detectors—can be applied for feedstock, processes monitoring, and quality control of biofuels (Mischnick and Momcilovic 2010);
• Spectroscopy and spectrometry identification and quantification of organic and inorganic compounds, polar and nonpolar, such as metals and by-products in biofuel synthesis, by means of radiation interaction or radiation production: nuclear magnetic resonance, Fourier transform infrared, X-ray diffractometry and fluorescence, ultraviolet and visible spectrophotometry, atomic absorption spectrometry (AAS), optical emission spectrometry—can be applied for feedstock, process monitoring, and quality control of biofuels (Shuo and Aita 2013; Orts et al. 2008);
• Mass spectrometry identification and quantification of organic compounds, by means of molecular fragmentation—can be applied for process monitoring, to verify the product purity, and for metabolic engineering approaches of microorganisms (Orts et al. 2008; Jang et al. 2012);
• Microscopy (e. g., scanning electron microscopy, transmission electron microscopy, and atomic force microscopy): observation of surface atomic composition and disposition of biomass components (morphology)—are frequently used for natural polymers and fibers (Hu 2008).
Table 6 presents some general uses of analytical techniques in chemical analysis of biomass for liquid biofuels production.
It is generally desirable to apply the highest possible number of techniques to obtain the greatest amount of information about a biomass. For example: Sugarcane could be analyzed by HPLC-refractive index detector to determine the sugar content, its molecular characteristics could be characterized by near-infrared spectroscopy, and its energy content by differential scanning calorimetry. This same analytical approach could be applied to an oil crop for biodiesel production: GC-flame ionization detector for content of fat acids and esters in is grains; nearinfrared spectroscopy for molecular characteristics, and differential scanning calorimetry for energy content.