The composition and structure of lignin in different tissues—phellem (cork), phloem and xylem (wood)—of Quercus suber was studied. Whole cell walls and their respective isolated milled lignins were analyzed by pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS), two-dimensional nuclear magnetic resonance spectroscopy (2D-NMR) and derivatization followed by reductive cleavage (DFRC). Different tissues presented varied p-hydroxyphenyl:guaiacyl:syringyl (H:G:S) lignin compositions. Whereas lignin from cork has a G-rich lignin (H:G:S molar ratio 2:85:13), lignin from phloem presents more S-units (H:G:S molar ratio of 1:58:41) and lignin from xylem is slightly enriched in S-lignin (H:G:S molar ratio 1:45:55). These differences were reflected in the relative abundances of the different interunit linkages. Alkyl-aryl ethers (β–O–4′) were predominant, increasing from 68% in cork, to 71% in phloem and 77% in xylem, as consequence of the enrichment in S-lignin units. Cork lignin was enriched in condensed structures such as phenylcoumarans (β-5′, 20%), dibenzodioxocins (5–5′, 5%), as corresponds to a lignin enriched in G-units. In comparison, lignin from phloem and xylem presented lower levels of condensed linkages. The lignin from cork was highly acetylated at the γ-OH of the side-chain (48% lignin acetylation), predominantly over G-units; while the lignins from phloem and xylem were barely acetylated and this occurred mainly over S-units. These results are a first time overview of the lignin structure in xylem, phloem (generated by cambium), and in cork (generated by phellogen), in agreement with literature that reports that lignin biosynthesis is flexible and cell specific.

The effectiveness of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) as a rapid analytical technique to get insight in wildfire-induced molecular alterations of the soil organic matter in Mediterranean Leptosols was examined. To this end, the topsoil of two slopes with adjacent patches of burnt and unburnt Maritime Pine (Pinus pinaster) and eucalypt plantations (Eucalyptus globulus) were sampled in the Serra de Lousã, central Portugal. Several differences were found between the neighbouring burnt and unburnt soils, both in thermal desorption and pyrolysis behaviour. Thermal desorption results showed large amounts of aliphatic compounds (both alkyl and carbohydrate-derived compounds), which may indicate the incorporation of fresh plant material or low wildfire severity. Pyrolysis at 500 °C revealed an increase of low molecular weight molecules for certain homologous series in fire-affected soils, suggesting the occurrence of thermal breakdown and cracking of long-chain components. In addition, the presence of several thermo-labile markers pointed to the low severity of the wildfire. Elemental analysis indicated marked fire-induced increases in TOC and TN for the pine stand as opposed to noticeable decreases for the eucalypt stands. Probably, this contrast between the two sites is not due to differences in direct fire effects (especially fire severity) but to indirect fire effects i.e. in particular needle/leaf fall from affected canopies.

O objectivo deste trabalho centrou-se na caracterização de aglutinantes usados em pinturas de cavalete, através das técnicas de cromatografia líquida de alta eficiência (HPLC) e da cromatografia gasosa acoplada à espectrometria de massa, com pirólise (Py-GC/MS). Os resultados foram complementados através da análise por micro-espectroscopia de infravermelho (µ-FTIR). Outro dos objectivos consistiu na mimetização dos processos de degradação que ocorrem em pinturas, através de envelhecimento artificial de filmes de tinta. Neste trabalho foram estudados três tipos de aglutinantes: gema de ovo, cola animal e óleo de linho. Foram preparados filmes de tintas com os aglutinantes puros e/ou misturas com diversos pigmentos, nomeadamente, azurite, vermelho de chumbo e branco de chumbo. A técnica de µ-FTIR possibilitou a identificação dos aglutinantes e dos pigmentos usados. Os resultados obtidos por HPLC, utilizando o método Pico-Tag, permitiram comprovar que esta é uma técnica útil na identificação de materiais proteicos. Através da análise das amostras contendo pigmentos e das amostras sujeitas ao envelhecimento artificial, verificou-se que estes dois factores influenciam a composição em termos da quantidade de aminoácidos e, consequentemente, a identificação dos aglutinantes. Uma limitação desta técnica é a análise de amostras contendo cobre, deste modo foi desenvolvido um método de remoção destes catiões, através da técnica de cromatografia de troca iónica, verificando-se ser eficiente. Através da técnica de HPLC foram ainda analisadas um conjunto de seis amostras do Retábulo Flamengo da Sé de Évora, uma amostra da camada de preparação de um escudo de aparato lacado do século XVI/XVII e uma amostra do retábulo de Ferreira do Alentejo. A técnica de GC/MS, realizada apenas em amostras não sujeitas ao envelhecimento artificial, permitiu identificar e caracterizar amostras em que o aglutinante usado era óleo. Por outro lado, em misturas de óleo e ovo, esta técnica mostrou-se eficiente na confirmação da existência dos dois tipos de aglutinantes.

Mulching has amply proven its effectiveness to mitigate post-fire soil erosion but its impacts on soil organic matter (SOM) quality and quantity continue poorly studied. The present study addressed this knowledge gap for a eucalypt plantation in central Portugal that had been burnt and, immediately after the wildfire, mulched with 13.6 Mg ha-1 of eucalypt logging residues some five years before. This was done by performing a range of analytical techniques (elemental and isotope analyses, analytical pyrolysis and 13C NMR spectroscopy) not only on the bulk soil samples but also on their humic acids (HAs) and free organic matter (FOM) fractions. While mulching reduced soil and SOM losses with 91 and 93%, respectively, it also improved SOM quality of the topsoil, in particular in terms of HAs and FOM. At 0-4 cm depth, both HAs and FOM contents were roughly twice as high in the mulched plots as in the control plots. The effects of mulching on the molecular composition of HAs and FOM fractions, however, varied markedly. Analytical pyrolysis (Py-GC/MS) revealed that mulching had led to a noticeable accumulation of labile, aliphatic SOM constituents such as carbohydrate-derived and alkyl compounds (fatty acids and n-alkanes) but that it hardly affected the composition of HAs. Even so, solid-state 13C NMR spectroscopy showed that mulching had resulted in a relative increase in aryl C in the FOM fraction, suggesting an enhanced preservation of the pyrogenic OM. Overall, the combined use of a range of analytical techniques allowed to conclude that, five years after their application, the forest logging residues had led to a greater preservation of the fire-derived pyrogenic OM (mainly aromatic compounds) in the topsoil as well as to higher contents of SOM's most labile molecular constituents (mainly carbohydrates and n-alkyl compounds). The former reflected the reduced erosion rates, while the latter was probably due to a combination of reduced erosion rates with the additional input of fresh organic matter.

Analytical pyrolysis is used to chemically study complex molecular materials and is applied in a wide range of fields. Pyrolysis is a thermochemical process associated to the breaking of chemical bonds using thermal energy, transforming a nonvolatile compound into a volatile degradation mixture. This chapter refers to analytical pyrolysis of lignocellulosic materials, i.e., when pyrolysis is used for chemical characterization, applied to samples with small particle sizes, at 500–650°C, and with short residence times. The reactions that occur during pyrolysis of the structural components are discussed regarding the mechanisms and the pyrolysis products obtained from cellulose, hemicelluloses, and lignin. A compilation of data is made on the characterization of lignocellulosic materials using Py-GC/FID(MS) or Py-GC/MS as analytical tools including woods and barks of several species. The pyrogram profiles and important parameters on lignin chemical composition such as the H:G:S relation and the S/G ratio are summarized. Analytical pyrolysis is a versatile methodology that may be applied to characterize the lignin directly on the lignocellulosic material or after isolation from the cell wall matrix (e.g., as MWL or dioxane lignin) or from pulps or spent liquors. It is therefore an excellent tool to study lignin compositional variability in different materials and along various processing pathways.

A mixture of beeswax and Dammar resin (in a ratio of 7 parts to 2 parts, respectively) prepared as an adhesive, was profusely used for fixing water gilding and tempera coatings on polychrome sculptures, in Portugal, in the second half of the twentieth century. This practice was the result of a conservation technology transfer that took place throughout northern Europe, namely throughout education and training of young restorers from abroad at Institut Royal du Patrimoine Artistique in Brussels. This type of treatment was challenged in the 1970’s. This paper presents the methodology used (from an archaeological perspective) to find again these substances on sculptures which have been impregnated with them, and show until which point it is possible to detect both wax and resin in the paint layers. The results obtained by micro Fourier transform infrared spectroscopy, and Pyrolysis-Gas Chromatography-Mass Spectrometry proved difficult to put in evidence the presence of the Dammar resin; a limit which is not without consequences for the historic and conservation assessment of our heritage.

O lodo resultante do tratamento de esgoto doméstico, gerado por processos aeróbios ou anaeróbios, nem sempre pode ser utilizado como fertilizante ou em compostagem devido à possível acumulação de compostos tóxicos e patógenos no solo. O processo de pirólise pode ser uma alternativa para obter produtos que podem ser utilizados como biocombustível ou matéria-prima nas indústrias. O objetivo deste trabalho foi realizar um estudo comparativo entre a pirólise térmica rápida de quatro amostras de lodo coletadas em períodos climáticos distintos, sendo: duas em período chuvoso (C1 e C3) e duas em período de estiagem (C2 e C4). Influências de fatores como presença de metais, teor de umidade, matéria orgânica e granulometria também foram observadas. Os testes pirolíticos foram feitos em um micropirolisador acoplado a um GC/MS a 450°C, 600°C e 750°C com granulometria em torno de 0,125 mm (120 mesh) para as duas primeiras coletas (C1 e C2). Enquanto que para as duas últimas (C3 e C4), além desta, foram analisadas amostras com granulometria em torno de 0,177 mm (80 mesh) e 0,354 mm (45 mesh). O desempenho dos experimentos foi avaliado quanto ao teor de compostos precursores de biocombustíveis e de hidrocarbonetos nos produtos de pirólise. As pirólises a 750°C das amostras coletadas em período chuvoso e com menor granulometria (0,125 mm) forneceram maiores percentuais de compostos precursores de biocombustíveis, sendo 21,9% para a coleta 1 e 42,6% para a 3. Menores granulometrias apresentaram melhores resultados em relação às outras. Nestas condições, para a coleta 3, foram obtidos 42,6% em compostos pré-combustíveis contra 38,8% para 0,177 mm e 40,2% para 0,354 mm, todos a 750 °C. Da mesma forma, para a coleta 4 (período de estiagem) foram obtidos 40,5% para 0,125 mm, 35,9% para 0,177 mm e 40,9% para 0,354 mm, na mesma temperatura. Além disto, também foi observado que a quantidade de umidade e metais principalmente Ca, K, Fe e Zn, podem ter contribuído para a diferença entre os resultados. As amostras de lodo coletado em período chuvoso apresentaram menores percentuais de oxigênio sendo 3,5% a 750°C para a coleta 1 e de 2,4% a 3,0% para as amostras da coleta 3, todas a 450°C. A redução na quantidade de oxigênio pode estar associada à ocorrência de reações de desoxigenação e descarboxilação proporcionando elevada produção de CO2, principalmente a 750°C. Os percentuais de nitrogênio foram próximos nas três temperaturas e granulometrias testadas, sendo menor a 600°C nos produtos gerados pelas coletas 1, 3 e 4. Portanto, as amostras coletadas em período chuvoso apresentaram maiores percentuais de hidrocarbonetos e compostos pré-combustíveis em relação às amostras das coletas em período de estiagem, provavelmente devido à baixa eficiência dos reatores UASB nestas condições climáticas.

Light is a determining factor in the discoloration of plastics, and photodegradation processes can affect the molecular structures of both the polymer and colorants. Limited studies focused on the discoloration of heritage plastics in conservation science. This work investigated the discoloration of red historical polyethylene (PE) objects colored with PR 48:2 and PR 53:1. High-density and low-density PE reference polymers, neat pigment powders, and historical samples were assessed before and after accelerated photoaging. The applied methodology provided insight into the individual light-susceptibility of polyethylenes, organic pigment lakes, and their combined effect in the photoaging of historical plastic formulations. After light exposure, both PE references and historical samples yellowed, PR53:1 faded, and PR 48:2 darkened; however, both organic pigments faded severely in the historical samples. This highlights the role played by the plastic binder likely facilitating the pigment photofading. Fourier transform infrared spectroscopy and mass spectrometry techniques—EGA-MS, PY-GC/MS, and TD-GC/MS—were successfully employed for characterizing the plastic formulations and degradation. The identification of phthalic compounds in both aged β-naphthol powders opens new venues for studies on their degradation. This work’s approach and analytical methods in studying the discoloration of historical plastics are novel, proving their efficacy, reliability, and potentiality.

This work presents the results of the analysis of the organic materials (red lakes and binders) from the flesh tones, wings, and vests of the angels from the mural paintings from the Charola of the Convent of Tomar. Pyrolysis coupled to gas chromatography and mass spectrometry (Py-GC/MS) was selected for the identification of binders, and liquid chromatography coupled to diode array and MS detection (LC/DAD/MS) was used for the identification of lakes in the red paint layers

This work aims at characterizing a group of lacquerware objects attributed to the region of Canton, in south China, some of which form part of the Portuguese royal collections dating from the 18th and 19th centuries. Laboratory analyses have allowed the identification of materials and manufacturing techniques of these objects. Analytical results have showed close correspondence with the accounts of merchants and travelers dating from that period.