Linkage Abundance and Molecular Weight Characteristics of Technical Lignins by Attenuated Total Reflection‐FTIR Spectroscopy Combined with Multivariate Analysis

Lignin is an attractive material for the production of renewable chemicals, materials and energy. However, utilization is hampered by its highly complex and variable chemical structure, which requires an extensive suite of analytical instruments to characterize. Here, we demonstrate that straightfor...

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Bibliographic Details
Published in:ChemSusChem Vol. 12; no. 6; pp. 1139 - 1146
Main Authors: Lancefield, Christopher S., Constant, Sandra, de Peinder, Peter, Bruijnincx, Pieter C. A.
Format: Journal Article
Language:English
Published: Germany Wiley Subscription Services, Inc 21.03.2019
John Wiley and Sons Inc
Subjects:
biomass
chemometrics
Coherence
Fourier transforms
FTIR spectroscopy
Infrared spectroscopy
Lignin
Mathematical models
Molecular weight
Multivariate analysis
NMR
Nuclear magnetic resonance
Organic chemistry
partial least squares modelling
Principal components analysis
Quantum phenomena
Reflection
Spectrum analysis
Streamlining
biomass
chemometrics
lignin
partial least squares modelling
FTIR spectroscopy
ISSN:1864-5631, 1864-564X, 1864-564X
Online Access:Get full text
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Summary:Lignin is an attractive material for the production of renewable chemicals, materials and energy. However, utilization is hampered by its highly complex and variable chemical structure, which requires an extensive suite of analytical instruments to characterize. Here, we demonstrate that straightforward attenuated total reflection (ATR)‐FTIR analysis combined with principle component analysis (PCA) and partial least squares (PLS) modelling can provide remarkable insight into the structure of technical lignins, giving quantitative results that are comparable to standard gel‐permeation chromatography (GPC) and 2D heteronuclear single quantum coherence (HSQC) NMR methods. First, a calibration set of 54 different technical (fractionated) lignin samples, covering kraft, soda and organosolv processes, were prepared and analyzed using traditional GPC and NMR methods, as well as by readily accessible ATR‐FTIR spectroscopy. PLS models correlating the ATR‐FTIR spectra of the broad set of lignins with GPC and NMR measurements were found to have excellent coefficients of determination (R2 Cal.>0.85) for molecular weight (Mn, Mw) and inter‐unit abundances (β‐O‐4, β‐5 and β‐β), with low relative errors (6.2–14 %) as estimated from cross‐validation results. PLS analysis of a second set of 28 samples containing exclusively (fractionated) kraft lignins showed further improved prediction ability, with relative errors of 3.8–13 %, and the resulting model could predict the structural characteristics of an independent validation set of lignins with good accuracy. The results highlight the potential utility of this methodology for streamlining and expediting the often complex and time consuming technical lignin characterization process. One stop shop: The structural characterization of technical lignins is typically challenging, requiring extensive, high‐end instrumentation such as high‐field NMR spectrometers and gel permeation chromatography equipment. For routine analyses we show that attenuated total reflectance‐FTIR spectroscopy combined with chemometric approaches, especially partial least squares regression, can provide equivalent information on molecular weight and interunit abundances in a fraction of the time.
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ISSN:1864-5631
1864-564X
1864-564X
DOI:10.1002/cssc.201802809