Complementary Analytical Liquid Chromatography Methods for the Characterization of Aqueous Phase from Pyrolysis of Lignocellulosic Biomasses

Abstract

In this work, two analytical liquid chromatography methods were developed and compared for the characterization of aqueous phases from pyrolysis of lignocellulosic biomasses. NanoLC electron ionization-mass spectrometry (EI-MS) represents a novel and useful tool for both separation and identification of semi/nonvolatile and thermolabile molecules. The use of nanoscale flow rates, the highly reproducibility, and high detailed information on EI spectra are the principal advantages of this technique. On the other hand, comprehensive 2D-LC, providing a two-dimensional separation, increases the overall peak capacity lowering the occurrence of peak coelutions. Despite the use of reversed phase modes in both dimensions, a satisfactory degree of orthogonality was achieved by the employment of a smart design of gradient elution strategies in the second dimension in combination with photodiode array detection (PDA) and atmospheric pressure chemical ionization-mass spectrometry (APCI-MS). Because of the absence of the preliminary extraction procedure, the fingerprint obtained for these samples results is independent of the extraction yield or contamination contrary to the gas chromatography-mass spectrometry (GC-MS) approach where a liquid-liquid extraction of the water phase is necessary. The main classes of identified compounds were phenols, ketones, furans, and alcohols. The synergistic information on the two powerful analytical approaches, e.g., NanoLC EI-MS and LC × LC, in the identification of such complex samples has never been investigated and fully benefit on the one hand from the superior degree of mass spectral information from EI-MS and on the other hand from enhanced LC × LC compound separation.

Chromatographic Methods Applied to the Characterization of Bio-Oil from the Pyrolysis of Agro-Industrial Biomasses

“…In view of the complexity of the samples, the comprehensive two-dimensional liquid chromatography (LC × LC) [150] in the same way as it happens for GC × GC becomes an important tool for characterizing bio-oils, because there is a large increase in the resolving power when compared to one-dimensional methods. Another great alternative is the use of micro HPLC columns that allow very small mobile phase flows, facilitating the coupling to more efficient detectors than conventional ones [151][152][153].…”

“…Tomasini et al [153] described a method for the characterization of aqueous phases from bio-oils of coconut fiber, sugarcane straw and sugarcane bagasse using comprehensive twodimensional liquid chromatography with detection by diode array followed by mass spectrometry with atmospheric pressure chemical ionization. Using this system, it was identified 26 compounds belonging to the classes of phenols, ketones, furans and alcohols.…”

“…The low flow used due to the nano-dimensions allows better coupling to mass detectors, including those with electron impact ionization, normally used for GC [153,244]. In the case of coupling a NanoLC with a mass spectrometer by electron impact (EI-MS), there is the advantage of compounds identification be performed by direct comparison with mass spectral libraries [153,244,245].…”

Ultra-high performance supercritical fluid chromatography hyphenated to atmospheric pressure chemical ionization high resolution mass spectrometry for the characterization of fast pyrolysis bio-oils

“…It was found that RPLC x RPLC had the potential of resolving up to 2000 peaks [7], highlighting the potential of this technique for the comprehensive analysis of the aqueous phase of the bio-oil. Both photo diode array (PDA) and MS detection were latter coupled to RPLC x RPLC and a more detailed analysis could be obtained [8]. Finally, an orthogonal separation system was also recently proposed involving both RPLC and, for the first time, SFC (RPLC x SFC) [9].…”

Comprehensive two-dimensional liquid chromatography–tandem mass spectrometry for the simultaneous determination of wine polyphenols and target contaminants

“…The coupling of similar columns (e.g., RP-LC×RP-LC) may offer superior resolution [13,14] when different mobile phase pH values [15][16][17] are utilized. This may also be implemented by varying the gradient composition between subsequent 2 D runs [18], according to the properties of the analytes being separated.…”