Determination of Phenolic Hydroxyl Groups in Lignin by Combined Use of 1H NMR and UV Spectroscopy
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Eija Tiainen
Summary
Two independent spectroscopic methods are presented and compared for the quantitation of the phenolic hydroxyl groups in lignins. The combined information is used to further elucidate the character of the lignin samples examined. The UV method is based on the difference of the spectroscopic properties of the ionised and the nonionised phenol. The method using 1H NMR spectroscopy is based on the exchange of phenolic protons in D2O. The difference in integrated proton intensities in the sample dissolved in DMSO and the sample with additional 20% D2O is proportional to the phenolic protons. The method based on UV spectroscopy uses differences in the maxima close to 300 nm and 350 nm of the sample dissolved in alkali and the neutral sample. The results using the two independent methods are in agreement for milled wood lignin, for kraft lignin and for model compounds carrying one aromatic hydroxyl group. For modified lignins and for model compounds with more than one aromatic hydroxyl group, the UV method gives too low values for phenolic hydroxyl groups. The combined results obtained by the two methods however provide information of the total amount of the phenolic groups and of the nature of the phenolic structure formed by the lignin refining.
Copyright © 1999 by Walter de Gruyter GmbH & Co. KG
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- Literature Reports
Artikel in diesem Heft
- The Significance of Accelerated Laboratory Testing Methods Determining the Natural Durability of Wood
- The Thermomechanical Behaviour of Wood Subject to Fungal Decay
- Fixation of Chromium in Wood from Trivalent Chromium Salt Solutions
- Spatial Distribution of Metal Ions in Spruce Wood by Synchrotron Radiation Microbeam X-Ray Fluorescence Analysis
- Chemical Composition of Lipophilic Extractives from Eucalyptus globulus Labill. Wood
- Antifungal Compounds in the Ethyl Acetate Soluble Fraction of the Extractives of Taiwania (Taiwania cryptomerioides Hayata) Heartwood
- Efficacy of Pinosylvins against White-Rot and Brown-Rot Fungi
- Investigations into Laccase-Mediator Delignification of Kraft Pulps
- Cell-Wall-Associated Oxidases from the Lignifying Xylem of Angiosperms and Gymnosperms: Monolignol Oxidation
- Atmospheric Acetic Acid Pulping of Rice Straw IV: Physico-Chemical Characterization of Acetic Acid Lignins from Rice Straw and Woods. Part 1. Physical Characteristics
- Lignin-Polyphenol Interaction in Azobe (Lophira alata) Heartwood. A Study on Milled Wood Lignin (MWL) and Klason Residues
- Electrospray Ionization Mass Spectrometry as a Tool for Lignins Molecular Weight and Structural Characterisation
- Determination of Phenolic Hydroxyl Groups in Lignin by Combined Use of 1H NMR and UV Spectroscopy
- The Effective Diffusion Coefficient and Mass Transfer Coefficient of Nordic Softwoods as Calculated from Direct Drying Experiments
- Stress Relaxation of Sugi (Cryptomeria japonica D.Don) Wood in Radial Compression under High Temperature Steam
- Structural Performance of Fire-Retardant Treated Plywood: Effect of Elevated Temperature
- Sorption Behaviour and Dimensional Changes of Wood-Coating Composites
- Literature Reports
