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An improved methodology for the quantification of uronic acid units in xylans and other polysaccharides
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.ORCID iD: 0000-0002-2900-4713
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2007 (English)In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 342, no 11, 1442-1449 p.Article in journal (Refereed) Published
Abstract [en]

Uronic acids can be quantified either by a colorimetric determination after treatment with concentrated sulfuric acid and carbazole or by gas chromatography after methanolysis and subsequent acetylation. Both methods suffer from incomplete hydrolysis, an unavoidable degradation of the products to be analysed, and an inability to separate and quantify different types of uronic acids. In the present work, the fundamental chemistry involved in the two methods has been evaluated, and some modifications to increase their accuracy are suggested. By combining the two methods, a complete quantification of all individual types of urome acids present in a sample can be achieved.

Place, publisher, year, edition, pages
2007. Vol. 342, no 11, 1442-1449 p.
Keyword [en]
uronic acid; carbazole; methanolysis; 4-O-methylglucuronic acid; galacturonic acid; glucuronic acid; hexenuronic acid; xylan
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:kth:diva-7714DOI: 10.1016/j.carres.2007.03.031ISI: 000248370800007Scopus ID: 2-s2.0-34250650112OAI: oai:DiVA.org:kth-7714DiVA: diva2:12820
Note

QC 20100702

Available from: 2007-11-23 Created: 2007-11-23 Last updated: 2016-12-19Bibliographically approved
In thesis
1. Xylan Reactions in Kraft Cooking: Process and Product Considerations
Open this publication in new window or tab >>Xylan Reactions in Kraft Cooking: Process and Product Considerations
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Xylan is the main hemicellulose in birch, eucalyptus, and most other hardwood species. During kraft pulping a series of chemical reactions and physical processes involving xylan takes place. The processes studied here are the following: dissolution, degradation, redeposition onto the fibres, side-group conversion, and cleavage of side groups off the xylan backbone. The side group in native xylan consists of methylglucuronic acid, which is partly converted into hexenuronic acid during kraft cooking. Hexenuronic acid affects the pulp in terms of increased brightness reversion and reduced bleachability. The kinetics of the side-group cleavage and conversion reactions were studied using various analytical tools. The study revealed that the most common methods for methylglucuronic acid quantifcation can be signifcantly improved in terms of accuracy. A modifcation and combination of two of the methods was suggested and evaluated.

In order to minimise the hexenuronic acid content, a common suggestion involves the use of a high cooking temperature. The kinetic study found that the degree of substitution of pulp xylan is only slightly affected by temperature, and that the observed effects are likely to be more associated with the xylan content of the pulp than with the hexenuronic acid content of the xylan. For the dissolved xylan, however, the degree of substitution indicated a high temperature dependency for birch kraft cooking.

By collecting black liquors at different stages in the cook, different molecular properties of the dissolved xylan was obtained. The liquors were charged at later parts of the cook, making the dissolved xylan to reattach to the fibres. Depending on the molecular properties of the added xylan, the tensile strength properties of the produced paper were improved. These improvements in paper properties were correlated to the molecular behaviour of the added xylan in solution.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. [11], 73 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2007:78
Keyword
Xylan, Kraft cooking, Paper strength, Sheet density, Methylglucuronic acid, Hexenuronic acid
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-4551 (URN)978-91-7178-819-1 (ISBN)
Public defence
2007-12-14, F3, Lindstedtsvägen 26, Stockholm, 10:00
Opponent
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Note
QC 20100702Available from: 2007-11-23 Created: 2007-11-23 Last updated: 2010-07-02Bibliographically approved

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Lindström, Mikael

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