Effect of pH on lignin analysis by Raman spectroscopy

Elina Warsta, Anni Lähdetie, Anna-Stiina Jääskeläinen, Tapani Vuorinen (Corresponding Author)

Research output: Contribution to journalArticleScientificpeer-review

6 Citations (Scopus)

Abstract

Ultraviolet resonance Raman (UVRR) spectroscopy is a powerful tool for structural lignin analysis in situ: modification or isolation of lignin from biomass is not necessary. UVRR spectroscopy is equally applicable for samples with high lignin content and those with very low lignin content. Monomeric phenolic lignin model compounds and wood pulp samples have been studied at neutral and alkaline pH with UVRR spectroscopy. Concentration of guaiacol correlated well with the relative Raman band intensity, which indicates that lignin-containing solutions can be quantitatively measured with UVRR spectroscopy. A change in pH induced a recordable shift in the aromatic band position in the spectra, which was 25–35 cm-1 with phenolic model compounds without para substitution, 8–12 cm-1 with phenolic model compounds with para substitution, and about 2–7 cm-1 with pulp samples. No shift was detected with a non-phenolic model compound. Increasing the amount of phenolic hydroxyl groups increased the UVRR band shift in pulp samples. Additionally, increasing the pH enhanced the relative aromatic band intensity in the UVRR spectra in solution of the phenolic model compound. Accordingly, pH adjustment is relevant prior to any lignin analysis with Raman spectroscopy.
Original languageEnglish
Pages (from-to)451-457
Number of pages7
JournalHolzforschung
Volume66
Issue number4
DOIs
Publication statusPublished - 2012
MoE publication typeA1 Journal article-refereed

Fingerprint

Lignin
Raman spectroscopy
Pulp
Substitution reactions
Guaiacol
Hydroxyl Radical
Raman scattering
Wood
Biomass

Keywords

  • lignin
  • lignin structure analysis
  • pH
  • phenolic hydroxyl group
  • UV resonance Raman (UVRR) spectroscopy

Cite this

Warsta, E., Lähdetie, A., Jääskeläinen, A-S., & Vuorinen, T. (2012). Effect of pH on lignin analysis by Raman spectroscopy. Holzforschung, 66(4), 451-457. https://doi.org/10.1515/hf.2011.176
Warsta, Elina ; Lähdetie, Anni ; Jääskeläinen, Anna-Stiina ; Vuorinen, Tapani. / Effect of pH on lignin analysis by Raman spectroscopy. In: Holzforschung. 2012 ; Vol. 66, No. 4. pp. 451-457.
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Warsta, E, Lähdetie, A, Jääskeläinen, A-S & Vuorinen, T 2012, 'Effect of pH on lignin analysis by Raman spectroscopy', Holzforschung, vol. 66, no. 4, pp. 451-457. https://doi.org/10.1515/hf.2011.176

Effect of pH on lignin analysis by Raman spectroscopy. / Warsta, Elina; Lähdetie, Anni; Jääskeläinen, Anna-Stiina; Vuorinen, Tapani (Corresponding Author).

In: Holzforschung, Vol. 66, No. 4, 2012, p. 451-457.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

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AB - Ultraviolet resonance Raman (UVRR) spectroscopy is a powerful tool for structural lignin analysis in situ: modification or isolation of lignin from biomass is not necessary. UVRR spectroscopy is equally applicable for samples with high lignin content and those with very low lignin content. Monomeric phenolic lignin model compounds and wood pulp samples have been studied at neutral and alkaline pH with UVRR spectroscopy. Concentration of guaiacol correlated well with the relative Raman band intensity, which indicates that lignin-containing solutions can be quantitatively measured with UVRR spectroscopy. A change in pH induced a recordable shift in the aromatic band position in the spectra, which was 25–35 cm-1 with phenolic model compounds without para substitution, 8–12 cm-1 with phenolic model compounds with para substitution, and about 2–7 cm-1 with pulp samples. No shift was detected with a non-phenolic model compound. Increasing the amount of phenolic hydroxyl groups increased the UVRR band shift in pulp samples. Additionally, increasing the pH enhanced the relative aromatic band intensity in the UVRR spectra in solution of the phenolic model compound. Accordingly, pH adjustment is relevant prior to any lignin analysis with Raman spectroscopy.

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Warsta E, Lähdetie A, Jääskeläinen A-S, Vuorinen T. Effect of pH on lignin analysis by Raman spectroscopy. Holzforschung. 2012;66(4):451-457. https://doi.org/10.1515/hf.2011.176