1064 nm dispersive multichannel Raman spectroscopy for the analysis of plant lignin

Title1064 nm dispersive multichannel Raman spectroscopy for the analysis of plant lignin
Publication TypeJournal Article
Year of Publication2011
AuthorsMeyer MW, Lupoi JS, Smith EA
Journal TitleAnalytica Chimica Acta
Date Published11
Type of ArticleArticle
ISBN Number0003-2670
Accession NumberWOS:000296755300017
Keywords1064 nm dispersive multichannel Raman spectrometer, biodegradation, cellulose, composition, enzymatic-hydrolysis, EXCITATION, explosives, Guaiacyl, intensity, Lignin monomer, p-Hydroxyphenyl, Partial least squares, spectrometer, Syringyl

The mixed phenylpropanoid polymer lignin is one of the most abundant biopolymers on the planet and is used in the paper, pulp and biorenewable industries. For many downstream applications, the lignin monomeric composition is required, but traditional methods for performing this analysis do not necessarily represent the lignin composition as it existed in the plant. Herein, it is shown that Raman spectroscopy can be used to measure the lignin monomer composition. The use of 1064 nm excitation is needed for lignin analyses since high fluorescence backgrounds are measured at wavelengths as long as 785 nm. The instrument used for these measurements is a 1064 nm dispersive multichannel Raman spectrometer that is suitable for applications outside of the laboratory, for example in-field or in-line analyses and using remote sensing fiber optics. This spectrometer has the capability of acquiring toluene/acetonitrile spectra with 800 cm(-1) spectral coverage, 6.5 cm(-1) spectral resolution and 54 S/N ratio in 10 s using 280 mW incident laser powers. The 1135-1350 cm(-1) and 1560-1650 cm(-1) regions of the lignin spectrum can be used to distinguish among the three primary model lignin monomers: coumaric, ferulic and sinapic acids. Mixtures of the three model monomers and first derivative spectra or partial least squares analysis of the phenyl ring breathing modes around 1600 cm are used to determine sugarcane lignin monomer composition. Lignin extracted from sugarcane is shown to have a predominant dimethoxylated and monomethoxylated phenylpropanoid content with a lesser amount of non-methoxylated phenol, which is consistent with sugarcane's classification as a non-woody angiosperm. The location of the phenyl ring breathing mode peaks do not shift in ethanol, methanol, isopropanol, 1,4 dioxane or acetone. Published by Elsevier B.V.

Alternate JournalAnal. Chim. Acta