Direct exposure electron ionization mass spectrometry and gas chromatography/mass spectrometry techniques to study organic coatings on archaeological amphorae

Two different analytical approaches, direct exposure electron ionization mass spectrometry (DE-MS) and gas chromatography/mass spectrometry (GC/MS), were compared in a study of archaeological resinous materials. DE-MS was found to be an efficient fingerprinting tool for the fast screening of organic archaeological samples and for providing information on the major components. GC/MS appeared to be more efficient in unravelling the sample composition at a molecular level, despite the long analysis time and the need for a wet chemical pretreatment. Both procedures were applied to characterize the organic material present as coatings in Roman and Egyptian amphorae. DE-MS successfully identified abietanic compounds, hence a diterpenic resinous material could be identified and its degree of oxidation assessed. GC/MS enabled us to identify dehydroabietic acid, 7-oxodehydroabietic acid, 15-hydroxy-7-oxodehydroabietic acid, 15-hydroxydehydroabietic acid, retene, tetrahydroretene, norabietatriene, norabietatetraene and methyl dehydroabietate. These oxidized and aromatized abietanes provided evidence that the amphorae examined were waterproofed with a pitch produced from resinous wood of plants from the Pinaceae family. The chemometric evaluation of the GC/MS data highlighted significant chemical differences between the pitches found in the two archaeological sites, basically related to differences in the production techniques of the materials and in their degradation pathways.     

Analysis of lignin from archaeological waterlogged wood by direct exposure mass spectrometry (DE-MS) and PCA evaluation of mass spectral data

The chemical characterisation of waterlogged archaeological wood is of fundamental importance to understand the degradation processes undergone by wooden objects and consequently to develop suitable consolidation and conservation procedures. Lignin extracted from archaeological waterlogged wood samples was characterized using direct exposure electron ionisation mass spectrometry (DE-MS). DE-MS achieves a mass spectral fingerprint of the sample in a few minutes, avoiding any chemical pre-treatment and requiring only few micrograms of material.Mass spectral data were put in relation to the chemical composition of lignin and evaluated by means of principal component analysis (PCA). The preliminary results, presented in this study, demonstrate the feasibility and the potential of DE-MS as a reproducible and rapid screening method for archaeological waterlogged wood samples.     

A multi-analytical study of degradation of lignin in archaeological waterlogged wood

Historical or archaeological wooden objects are generally better conserved in wet environments than in other contexts. Nevertheless, anaerobic erosion bacteria can slowly degrade waterlogged wood, causing a loss of cellulose and hemicellulose and leading to the formation of water-filled cavities. During this process, lignin can also be altered. The result is a porous and fragile structure, poor in polysaccharides and mainly composed of residual lignin, which can easily collapse during drying and needs specific consolidation treatments. For this reason, the chemical characterization of archaeological lignin is of primary importance in the diagnosis and conservation of waterlogged wood artifacts. Current knowledge of the lignin degradation processes in historical and archaeological wood is extremely inadequate. In this study lignin extracted from archaeological waterlogged wood was examined using both Py-GC/MS, NMR spectroscopy and GPC analysis. The samples were collected from the Site of the Ancient Ships of San Rossore (Pisa, Italy), where since 1998 31 shipwrecks, dating from 2nd century BC to 5th century AD, have been discovered. The results, integrated by GPC analysis, highlight the depolymerization of lignin with cleavage of ether bonds, leading to an higher amount of free phenol units in the lignin from archaeological waterlogged wood, compared to sound lignin from reference wood of the same species.     

Degradation of lime wood painting supports: Evaluation of changes in the structure of aged lime wood by different physico-chemical methods

In the present work, aged lime wood from painting supports, differing in terms of the provenance, conservation status, wood ages and of storage conditions (microclimate in churches or rooms) was analysed, applying analytical pyrolysis as the main method. Analytical pyrolysis combined with gas chromatography/mass spectrometry has shown a great potential as a fast, sensitive and good reproducible analytical tool to characterize the structure of a variety of natural polymers. The attraction of the application of analytical pyrolysis for the investigation of objects having the artistic value is connected with the use of minor amounts of samples for analysis. Carbohydrates and lignin compounds released under Py-GC/MS were analysed, and carbohydrate/lignin (C/L) and syringyl/guaiacyl (S/G) ratios were determined. On the basis of the results obtained, it can be concluded that, with ageing of lime wood the carbohydrates moiety decreases significantly as the result of degradation of hemicelluloses, namely, slow hydrolysis of O-acetyl groups of xylan with the release of acetic acid. The increase in the free radical concentration in aged wood in comparison with the reference sample, observed by ESR-spectroscopy, confirms the relative increase in the lignin content and the degradation of lignin–carbohydrate complexes. The S/G ratio did not show any preference in the degradation of S or G lignin of aged lime wood. The main trends in changes in parameters of the porous structure of the objects under investigation are in conformity with the alteration in the composition of wood complex. Summing up the data of Py-GC/MS and ESR-spectroscopy, it may be concluded that, for 180- and 270-year aged wood samples, some tendency for the alteration of the lignin matrix is observed, namely, an increase in condensity, accompanied by the development of polyconjugated systems.     

Pyrolysis-GC/MS and TG/MS study of mediated laccase biodelignification of Eucalyptus globulus kraft pulp

Biobleaching studies using laccase mediator system (LMS) were carried out, under optimized conditions, on two unbleached Eucalyptus globulus kraft pulps, one produced by conventional way, with kappa number of 16.1, and another with kappa number of 14.5, obtained by modified kraft procedure with a high liquor/wood ratio and with black liquor replacement in the middle of the cooking. The pulp properties before and after LMS and alkaline extraction were evaluated in terms of kappa number, hexeneuronic acid content, viscosity, brightness and acid insoluble lignin content.The original milled wood sample and the kraft pulps were characterized by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetry/mass spectrometry (TG/MS). Eucalypt wood lignin produces guaiacol and syringol derivatives during pyrolysis. These lignin products can be detected with high sensitivity using the selected ion chromatograms even in the bleached pulp of low lignin content (about 0.5%). Py-GC/MS revealed that the lignin moieties were similarly altered during biobleaching as during pulping, which is exemplified by the preferential removal of aldehyde groups from the alkyl side groups. Semi-quantitative analysis of the pyrograms indicates that the lignin content of the biobleached pulps is reduced by about half in comparison with the unbleached pulps. The TG/MS results show that the hemicellulose content of wood was strongly modified during pulping resulting in higher thermal stability.     

Pyrolysis of lignin extracted from prairie cordgrass,aspen, and Kraft lignin by Py-GC/MS and TGA/FTIR

A study is undertaken to assess the effectiveness of lignin extracted from prairie cordgrass as a pyrolysis feedstock. The effects of variability of lignin source on fast and slow pyrolysis products are also investigated. To accomplish these goals, Py-GC/MS and TGA/FTIR are employed in the pyrolysis of three types of lignin: prairie cordgrass (PCG) lignin extracted from prairie cordgrass, aspen lignin extracted from aspen trees (hardwood), and synthetic Kraft lignin. Fast pyrolysis results from Py-GC/MS show that for PCG lignin, only ten of the detected compounds have relative peak area percentiles that exceed 2% and make up over 52% of the total area. For aspen lignin, excluding butanol that is used in the extraction process, only eight compounds are found to have relative peak areas exceeding 2% that make up over 52% of the total area. For Kraft lignin, only eight compounds exceeding 2% are found to make up more than 45% of the total area. Both techniques, Py-GC/MS and TGA/FTIR, indicate that PCG lignin releases more alkyls than aspen and Kraft lignin. TGA/FTIR results indicate that PCG lignin also releases by far the most light volatile products (<200 °C) while producing the least amount of char among the three types of lignin studied. These characteristics make PCG lignin a good choice in producing good quality bio-oil and thus decreasing upgrade requirements. Py-GC/MS results conclude that aspen lignin produces significantly more pyrolytic products than PCG lignin. This is indicative of the potential of aspen lignin to result in higher conversion rates of bio-oil than the other two lignins.     

Discrimination of genetically modified poplar clones by analytical pyrolysis–gas chromatography and principal component analysis

Analytical pyrolysis combined with gas chromatography and mass spectrometry (Py-GC–MS) is a relatively rapid (1–3 h) method for the investigation of polymers. Various wood tissues from transgenic poplar clones and from control samples have been subjected to a screening test by Py-GC–MS. Pyrolysis products from lignin- and carbohydrate-derived pyrolysis products were subjected to multivariate principal component analysis (PCA). The first three PC accounting for 39–72% of the total variance in the original data set could be attributed to vinyl products from lignin and levoglucosan from cellulose. Samples with gene construct rbcs-rol C were only discriminated by plotting PC1 versus PC3 using the whole data set. However, the wood from trees containing gene construct 35 S-rol C were discriminated in all examined models indicating significant impacts during biosynthesis of the wood. One sample within the data set was further clustered because it turned out that this tree died off after two vegetation periods.     

Py-GC/MS characterization of a wild and a selected clone of Arundo donax,and of its residues after catalytic hydrothermal conversion to high added-value products

Two analytical procedures based on gas chromatography and mass spectrometry were used to study the compositions of a wild population and a selected clone (Torviscosa) of giant reed (Arundo donax L.), one of the most promising biomass both in terms of energy and fine chemicals production. Gas chromatography/mass spectrometry (GC/MS) was used to characterize and quantitatively determine the monosaccharide composition. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), using hexamethyldisilazane (HMDS) as a derivatising agent, was used to characterize the lignocellulosic polymers. Analytical pyrolysis was also used to study the composition of residues left after the catalytic hydrolysis used to convert cellulose to levulinic acid and hemicellulose to furfural.GC/MS allowed us to determine the monosaccharide composition and polysaccharide content of the giant reed samples, highlighting that there was no significant difference between the wild population and the selected clone. GC/MS also highlighted that the giant reed leaves have a higher percentage (roughly 60%) of polysaccharide material than the stalks, which contain approximately 50%.Py-GC/MS, following the disappearance of the pyrolysis products of polysaccharides, showed that 150 °C and 190 °C are the best temperatures to obtain the complete catalytic conversion of hemicellulose and cellulose, respectively. Analytical pyrolysis also highlighted that in the course of catalytic hydrothermal conversion a partial depolymerisation of lignin was obtained. In particular, the formation of lignin units containing free phenol groups via the cleavage of the β-aryl ether bonds was demonstrated. The presence of these free phenols in the lignin network suggests the possible exploitation of lignin residues as antioxidant components or in high value biopolymer industries rather than the traditional use as low-value fuel for energy production.     

In situ modification of pyrolysis products of macromolecules in an analytical pyrolyser

An application of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) is presented for the fast on-line testing of solid catalysts activity in upgrading pyrolysis oils and/or gases of natural and synthetic polymers. Evaluation of the chemical conversion by a catalyst is simply and quickly performed in a Py-GC/MS instrument without any modification either of the micropyrolyser or the GC inlet. The pyrolysis products evolved from the sample pass through catalyst microbeds of some mm length and the GC/MS analysis of the converted products is performed on-line. Modification of polyolefin, styrene copolymer, polyester, polyamide, brominated epoxy resin and wood pyrolysate was carried out applying sodium type zeolite and medium acidic mesoporous aluminosilicate in the microbeds. The primary pyrolysis products are converted over the microbeds due to the catalytic activity of the bed material. Intramolecular hydrogen transfer reactions promoted by Na zeolite results in the isomerisation of alkenes and alkadienes evolved by pyrolysis from polyethylene and polypropylene. These basic catalysts were found to be effective for the elimination of brominated phenols from the pyrolysate of brominated epoxy resin. Cracking of alkane and alkene oligomer products of polyolefins to light isoalkenes occur over acidic mesoporous aluminosilicate. Certain compounds with polar groups evolved from polyester, polyamide, cellulose or lignin are removed by this catalyst. Alkenylaromatic compounds are simultaneously hydrogenated and polyaromatised in pyrolysis oils of styrene copolymers over both acidic and basic aluminosilicate catalysts tested.     

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

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. Copyright © 2015 John Wiley & Sons, Ltd.     

文物中多糖类胶结材料的热裂解-气相色谱/质谱识别

热裂解-气相色谱/质谱(Py-GC/MS)技术能够实现微量样品中有机组分的准确、快速检测,非常适用于文物中各类天然有机材料的定性分析。该研究以中国古代书画、建筑、器物等文化遗产中常用的淀粉、桃胶,以及西方文化遗产中常用的阿拉伯胶等多糖类胶结材料为研究对象,系统分析并总结各类材料的Py-GC/MS特征裂解组分及辨别方法。研究发现,淀粉、桃胶、阿拉伯胶在色谱保留时间前段的裂解产物基本一致,主要是小分子呋喃、酮类组分;在保留时间中段3类材料的裂解产物主要是呋喃型酮等组分,但不同材料的具体裂解组分差异明显;在保留时间后段,3类材料检出多种单糖衍生物以及单糖低聚体衍生物,其中桃胶与阿拉伯胶裂解组分较为接近,但与淀粉完全不同。因此,可根据不同保留时间段淀粉、桃胶、阿拉伯胶裂解产物的差异实现3类材料的辨别,其中1,6-脱水-β-D-吡喃葡萄糖只在淀粉中检出且色谱峰强度高,可以作为识别淀粉的特征组分;此外,可根据桃胶、阿拉伯胶在保留时间后段的裂解产物主要质谱碎片离子m/z 60、m/z 101的提取离子流图分布特征实现其辨别。基于所建立的Py-GC/MS方法,研究推断故宫旧藏清代剔红云龙纹天球瓶瓶口部...     

生物质主要组分低温热解研究

利用热重分析仪和裂解气质联用仪进行生物质主要组分低温热解特性研究。热重实验结果表明,生物质主要组分的热稳定性为：纤维素>木质素>半纤维素。半纤维素主要热解温度在210℃～320℃,而纤维素和木质素的主要热解温度分别在310℃～390℃和200℃～550℃。裂解气质联用实验考察不同温度对生物质主要组分低温热解产物的影响。半纤维素热解产物主要有乙酸、1-羟基-丙酮和1-羟基-2-丁酮,纤维素热解产物主要包括左旋葡聚糖和脱水纤维二糖,而木质素热解产物主要是邻甲氧基苯酚。     

Evidence for demethylation of syringyl moieties in archaeological wood using pyrolysis-gas chromatography/mass spectrometry

Archaeological oak (Quercus sp.) wood samples, ranging from 16(th) C. AD to 6000 BP, were studied using flash pyrolysis-gas chromatography/mass spectrometry to obtain insight into angiosperm lignin degradation. The pyrolysates revealed evidence of a number of 3-methoxy-1,2-benzenediol derivatives, methoxycatechols, directly related to 2,6-dimethoxyphenol, syringyl, moieties which are characteristic building blocks of angiosperm lignin. Mass spectra and mass chromatograms of these compounds are reported. The finding of these characteristic pyrolysis products in well-preserved archaeological wood provides unequivocal evidence that demethylation of syringyl units occurs very early in wood degradation. It is highly likely that the absence of abundant 3-methoxy-1, 2-benzenediols in degrading plant materials containing angiosperm lignin relates to the lability of these newly formed moieties.     

Application of pyrolysis-gas chromatography/mass spectrometry to study changes in the organic matter of macro- and microaggregates of a Mediterranean soil upon heating

The heating effect on the soil organic matter (SOM) of a Mediterranean soil was studied in two fractions (macro- and microaggregates) and in two environments (soil under canopy of Quercus coccifera and bare soil between plants). Samples were heated under laboratory conditions at different temperatures (220, 380 and 500°C) to establish their effects on the SOM quality and quantity by comparison with unheated control samples (25°C). The SOM content in the soil under canopy was higher than in the bare one and in the microaggregate fractions than in the macroaggregate ones. Increasing temperatures caused, in general, the decrease of SOM content in both soils as well as in both aggregate classes. The quality of SOM was determined after extraction with 0.1 M NaOH and analysed by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Obtained pyrolysates were characterized by the presence of polyphenols and other aromatic pyrolysis products (lipids, polysaccharides, proteins and lignin derivatives). Some of the products in these control samples, and furthermore the presence of black carbon (BC) markers (e.g. benzene, pyridine and toluene), confirmed the occurrence of past wildfires in the study zone. The composition of the SOM extracted from the soils heated at 220°C, was quite similar to that obtained from unheated soils. The products derived from polysaccharides and lignin, and some coming from polyphenols, were not detected in the pyrolysates of the soil heated at 380 and 500°C.     

食品级聚碳酸酯的热释放成分和热分解机理研究

利用程序控温式热裂解-气相色谱/质谱联用技术研究了4种聚碳酸酯(PC)样品在加热情况下的释放物化学成分.分别考察了4个解吸温度和5个裂解温度下PC的降解产物.结果发现在200℃时PC粒料中就有小分子化学物质释放出来,随温度升高,释放和分解出的小分子化学成分的种类和数量都愈加增多,主要成分为酚端基化合物;由不同聚合工艺合成的聚碳酸酯中释放的化学成分有很大的差别.同时通过分析PC的裂解产物成分,阐述了其热分解机理.升温过程中PC分子链发生断裂和重排生成多种以酚类为主的小分子化合物.     

On the interaction of HBT with pulp lignin during mediated laccase delignification—a study using fractionated pyrolysis-GC/MS

An analytical method using fractionated pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was developed and applied for characterizing the type of interaction between 1-hydroxybenzotriazole (HBT)-mediator and pulp lignin in laccase delignification of pulp. In fractionated pyrolysis, the sample is pyrolyzed at progressively increasing temperatures in order to study particular fractions of the sample and to minimize secondary pyrolysis effects. This makes it possible to determine whether a certain pyrolysis product originates from one chemical moiety or different chemical moieties in one molecule. In the present method, samples were fractionated by thermal desorption at 200 °C followed by pyrolysis at progressively increasing temperatures from 320 to 800 °C. The products formed in each fraction were separated in a capillary GC column and detected and identified using MS. The type of interaction between HBT and pulp lignin was studied by following the formation of nitrogen-containing products during fractionated pyrolysis of a residual lignin isolated from laccase/HBT-treated oxygen-delignified softwood kraft pulp. This residual lignin was found to contain approximately 2% HBT residue. Most (87%) of this residue was covalently linked to the residual lignin. The results also strongly suggest that the HBT residue is present in two chemically different forms.     

THM PyGC–MS of wood fragment and vegetable fibre forensic samples

Wood fragments and vegetable fibres were investigated using thermally assisted hydrolysis and methylation with pyrolysis gas chromatography–mass spectrometry (THM PyGC–MS). Multiple ion chromatography was used to decrease the interference from cellulosic peaks, and to obtain greater resolution between the lignin peaks. Forty-four wood samples were analysed using THM PyGC–MS. The wood fragments were able to be differentiated into angiosperms (hardwoods) and gymnosperms (softwoods) using principle component analysis (PCA), hierarchical cluster analysis (HCA), and the ratio of syringyl to guaiacyl lignin fragments (S/G ratio). PCA and HCA also differentiated several Monterey pine samples from the rest of the gymnosperms, primarily by the presence of β-pinene, an extractive compound. Other gymnosperm species and the individual angiosperm species were unable to be differentiated. A pilot study investigating the use of THM PyGC–MS for the analysis of vegetable fibres in forensic science found that the fibre types tended to group into two clusters, with one containing cotton, hemp and linen; and the other consisting of hessian, sisal, jute and coir. The seagrass sample was able to be differentiated from both groups. These groups were well separated using PCA, HCA and by the ratio of cinnamyl phenolic derivatives to guaiacyl lignin derivatives (C/G ratio). Some grouping of each fibre type was evident within each cluster, however the separation between the clusters was insufficient to differentiate them using these statistical techniques. THM PyGC–MS of vegetable fibres showed some potential for future use in forensic science.     

Discrimination of Thermoplastic Polyesters by MALDI-TOF MS and Py-GC/MS

The aim of this work is to discriminate thermoplastic polyester-polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polytrimethylene terephthalate (PTT), which cannot be easily identified by many methods. Both matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) were applied to identify these polyesters owing to their analytical ability to determining polymers' chemical structure. The three thermoplastic polyesters can be easily distinguished by MALDI-TOF MS according to their different repeated units. Py-GC/MS was used to analyze their specific pyrolyzates. The three polyesters can be identified through their characteristic pyrolysis products as well.     

Identifying acetylated lignin units in non-wood fibers using pyrolysis-gas chromatography/mass spectrometry

A series of non-wood plant fibers, namely kenaf, jute, sisal and abaca, have been analyzed upon pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) of the whole material. The pyrolysis products mainly arise from the carbohydrate and lignin moieties of the fibers. The lignin-derived phenols belonged to the p-hydroxyphenylpropanoid (H), guaiacylpropanoid (G) and syringylpropanoid (S) structures, and showed a high S/G ratio of between 2.0 and 5.4, the highest corresponding to kenaf. Among the lignin-derived phenols released, small amounts of sinapyl and coniferyl acetates (in both cis- and trans-forms) were identified for the first time upon Py-GC/MS of lignocellulosic materials. Acetylation of the sinapyl and coniferyl alcohols was at the gamma-position of the side chain. The release of these alcohols derived from intact acetylated lignin units upon pyrolysis seems to indicate that the native lignin in the fibers selected for this study is at least partially acetylated. Sinapyl (and coniferyl) acetates have recently been suggested to be authentic lignin precursors involved in the polymerization of lignin along with the normal sinapyl and coniferyl alcohols. Py-GC/MS will offer a convenient and rapid tool for analyzing naturally acetylated lignins, as well as to screen plant materials for the presence of acetylated units in lignin.     

Ultrafiltration and Pyrolysis Gas Chromatography Mass Spectrometry of Chlorolignins in Pulp Mill Effluent

Abstract

Investigations on the effluent of a German pulp mill on the river Rhine using ultrafiltration and pyrolysis gas chromatography mass spectrometry have shown the presence of several chlorinated 2-methoxyphenols, which probably originate from chlorinated lignin or lignosulfic acid. Chlorinated phenolic pyrolysis products identified were 2-methoxy-6-chlorophenol, 2-methoxy-4-methyl-6-chlorophenol, 2-methoxy-dichlorophenol, 2-methoxy-4-vinyl-6-chlorophenol, 2-methoxy-4-(chloropropyl)phenol, 2-methoxy-4-(prop-2-enyl)-6-chlorophenol, 2-methoxy-4-(propan-2-one)-6-chlorophenol, 2-methoxy-3, 5, 6-trichlorophenol, 2-methoxy-4-vinyl-3, 5, 6-trichlorophenol. Monochlorinated 2-methoxyphenols were the dominant chlorinated pyrolysis products, smaller amounts of di- and trichloromethoxyphenols were also detected. 2-Methoxyphenols (guaiacols) were the dominant lignin pyrolysis products, only small amounts of 2, 6-dimethoxyphenols (syringols) were detected. This indicates the origin from soft wood. A Py-(GC)-(MS)-TIC-chromatogram of reference spruce milled wood lignin is comparable with the TIC-chromatogram of pulp mill effluent MW-fraction > 10,000, showing many similar compounds. The ultrafiltration fraction 1000 < MW < 10,000 showed a remarkably empty TIC-chromatogram, with 2-methoxyphenol and 2-methoxy-6-chlorophenol as the only significant phenolic peaks. This may indicate a high degree of oxidation/chlorination of lignin in this fraction.