Snapshots of lignin oxidation and depolymerization in archaeological wood: an EGA‐MS study

Abstract

Evolved gas analysis-mass spectrometry (EGA-MS) was used for the first time to study archaeological wood, in order to investigate its chemical degradation. The archaeological wood was from an oak pile from a stilt house found in the Neolithic 'La Marmotta' village (Lake Bracciano, Rome, Italy). The sampling was performed from the external to the internal part of the pile, following the annual growth rings in groups of five. In addition, sound oak wood and isolated wood components (holocellulose and cellulose) were also analyzed, and the results were used to highlight differences because of degradation. Our study demonstrated that EGA-MS provides information on the thermo-chemistry of archaeological wood along with in-depth compositional data thanks to the use of MS. Our investigations not only highlighted wood degradation in terms of differences between carbohydrates and lignin content, but also showed that lignin oxidation and depolymerization took place in the archaeological wood. Mass spectral data revealed differences among the archaeological samples from the internal to the external part of the pile. An increase in the formation of wood pyrolysis products bearing a carbonyl group at the benzylic position and a decrease in the amount of lignin dimers were observed. These were related to oxidation and depolymerization reactions, respectively.

Recent Advances in Analytical Pyrolysis to Investigate Organic Materials in Heritage Science

“…Although the EGA system is arelatively new approach, it has already been used to investigate highly chemically complex materials such as synthetic polymers and lignocellulosic materials. [32] This technique provides information both on the thermochemistry and thermo-complexity (EGA) of as ample along with detailed compositional data and compound distribution (MS).…”

Термогравиметрический Анализ Образцов Ископаемой Древесины

“…(Таблица 2). По-видимому, это вызвано тем, что в процессе длительной экспозиции происходит окисление и деполимеризация лигнина, сопровождающаяся снижением содержания димеров лигнина [2,5]. Древесина дуба характеризовалась наличием плеча на кривой ДТГ с точкой перегиба при 282С, что, вероятно, обусловлено деструкцией термолабильных компонентов  гемицеллюз.…”

“…В данном процессе затрагивается и лигнин, процесс деградации которого изучен недостаточно [2,3]. В результате образуется пористая и хрупкая структура, с небольшим количеством полисахаридов и состоящая в основном из остаточного лигнина, который легко разрушается в процессе высыхания.…”

Sustainable Electrochemical Depolymerization of Lignin in Reusable Ionic Liquids

“…Importantly, structural isomers have been reported in the complex mixtures and most likely resulted from different degradation reactions 40 and lignin structural diversities 41 . Therefore, separation techniques such as high-performance liquid chromatography (HPLC) 42, 43, 56 or gas chromatography (GC) 57–59 were required to separate structural isomers resulting from untargeted conversions. The ideal analytical methodology for successful characterization of lignin decomposition processes therefore comprises a conversion detection technique (GPC, FTIR), a technique for deducing structural information (MS, NMR) and a separation method to deconvolute the isobaric and isomeric content.…”