Using Raman Spectroscopy to Identify Chromophores in Lignin—Lignocellulosics

Agarwal, Umesh P.; Atalla, R.H.

doi:10.1021/bk-2000-0742.ch011

Cited by 25 publications

(27 citation statements)

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“…ing through C5 is also possible, but this possibility is more typical for DHPs than for native lignins. Raman bands associated with ethylenic units of coniferaldehyde and coniferyl alcohol in lignin-containing materials have been identified (Agarwal and Atalla 1993;Agarwal et al 1995;Agarwal 1999;Agarwal and Atalla 2000). These data are summarized in Table 1.…”

Section: Raman Spectroscopymentioning

confidence: 97%

“…A number of FT-Raman applications to the field of lignocellulosics have been reported (Evans 1991;Scheepers et al 1993;Agarwal and Ralph 1997;Yamauchi et al 1997;Holmgren et al 1999;Niemelä et al 1999;Ona et al 1999;Yang et al 1999;Proniewicz et al 2002;Agarwal et al 2003Agarwal et al , 2005Edwards et al 2003;Yamauchi and Kurimoto 2003;Agarwal and Landucci 2004;Vester et al 2004;Yamauchi et al 2005). Moreover, Raman spectroscopy has a high sensitivity to detecting aromatic-ring conjugated groups (Schmid and Brosa 1971;Schmid and Topsom 1981;Agarwal and Atalla 2000;Agarwal et al 2005), which in lignin are present in small concentrations. Accordingly, the technique seems to be very well suited to quantifying such groups.…”

Section: Introductionmentioning

confidence: 99%

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Determination of ethylenic residues in wood and TMP of spruce by FT-Raman spectroscopy

Agarwal

Ralph

2008

HFSG

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A method based on FT-Raman spectroscopy is proposed for determining in situ concentrations of ethylenic resi dues in softwood lignin. Raman contributions at 1133 and 1654 cm -1 , representing coniferaldehyde and coni feryl alcohol structures, respectively, were used in quan tifying these units in spruce wood with subsequent conversion to concentrations in lignin. For coniferalde hyde units, the intensity of the 1133 cm -1 peak was measured in the difference spectrum obtained by sub tracting the bleached-wood spectrum from that of the unbleached. In the case of coniferyl alcohol residues, the intensity of the 1654 cm -1 band was calculated from the spectrum of extensively bleached wood. The concentra tions of coniferaldehyde and coniferyl alcohol units in spruce lignin were found to be 3.8% and 3.4%, respec tively, and were in good agreement with values deter mined by conventional techniques. This quantification of the ethylenic residues was based on the Raman inten sities of 1% coniferaldehyde and 1% coniferyl alcohol in bleached softwood kraft pulp. Initially, as background for this work, a number of suitable lignin model compounds and a softwood lignin model polymer (G-DHP) were used to calibrate the Raman method and demonstrate that the Raman technique was well suited for quantification of ethylenic structures. Experimental results demonstrated that thermomechanical pulping reduced the concentra tions of coniferaldehyde and coniferyl alcohol residues in comparison to wood by 28% and 24%, respectively.

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Section: Raman Spectroscopymentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Determination of ethylenic residues in wood and TMP of spruce by FT-Raman spectroscopy

Agarwal

Ralph

2008

HFSG

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“…o-Quinone has the most prominent Raman frequency at 1559 cm y1 , p-quinone at 1670 cm y1 when excited with 514.5 nm and measured in CH 2 Cl 2 solution (Agarwal and Atalla 2000). The most important residual chromophoric structures in the pulps are quinones and conjugated structures.…”

Section: Assignment Of Raman Bands and Comparison Of Results From Vismentioning

confidence: 99%

Resonance Raman spectroscopy of highly fluorescing lignin containing chemical pulps: Suppression of fluorescence with an optical Kerr gate

Saariaho¹,

Jääskeläinen²,

Matousek³

et al. 2004

Holzforschung

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Raman spectroscopy using 400 nm excitation was successfully applied to chemical pulp samples and the fluorescence background that usually limits the application of this method to such samples was effectively suppressed. This enabled the detection of much weaker Raman bands from the pulps. The rejection ratio of the fluorescence background to Raman scattering was estimated to be about 250. The resonance Raman spectra of peroxide bleached chemical pulps had chromophoric lignin bands at 1605 and 1655 cm y1 , whereas the chlorine dioxide bleached pulps had only the aromatic band at 1605 cm y1 . The square root of the aromatic chromophore band relative to cellulose band correlated linearly with the brightness which is in accordance with the Kubelka-Munk theory. This correlation indicated that the resonance enhanced Raman bands were mainly due to chromophoric lignin structures. Chlorine dioxide and peroxide bleached pulps gave different correlations to brightness, which was an indication of different kinds of chromophores in these pulps. The intensity of the aromatic band relative to the cellulose band was about 20 times higher with the ultraviolet (257 nm) than with the visible (400 nm) excitation. This clearly illustrated the importance of working with different excitation wavelengths. On one hand the UV excitation is more sensitive towards aromatic residual lignin in pulp, and on the other hand the visible excitation enables the selective detection of chromophoric lignin structures.

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“…43,49 Lignin is also characterized by various morphological methods such as thermal analysis and Raman/infrared (IR) analysis. [50][51][52] The chemistry and material properties of lignin has been reviewed extensively 30,31,[53][54][55] as well as chemical methods for modifying and blending it. [56][57][58][59][60][61] In this review, the authors present a brief survey lignin sources, chemistry and processing, as these issues directly impact its incorporation in modern polymeric materials, then review advances in covalent modifi cation and blending of lignin with many synthetic and natural polymers.…”

Section: Introductionmentioning

confidence: 99%

Chemistry of lignin-based materials

2013

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There is a need for renewable resources as a raw material for commodity polymers. Lignin is one of the most important natural biopolymers from renewable resources due to its suffi cient supply, robust material properties and the fact that its use does not compete with the food supply. Lignin has been investigated since the late 19th century, but its applications are limited due to poor processability, low reactivity and intrinsic heterogeneity depending on the plant source and isolation methods used. Current strategies for using lignin in modern materials center on integrating it with other natural or synthetic polymers. This review article introduces the technological importance of lignin and focuses on copolymers and blends based on lignin in a broad range of applications.

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Using Raman Spectroscopy to Identify Chromophores in Lignin—Lignocellulosics

Cited by 25 publications

References 0 publications

Determination of ethylenic residues in wood and TMP of spruce by FT-Raman spectroscopy

Determination of ethylenic residues in wood and TMP of spruce by FT-Raman spectroscopy

Resonance Raman spectroscopy of highly fluorescing lignin containing chemical pulps: Suppression of fluorescence with an optical Kerr gate

Chemistry of lignin-based materials

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