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TAPPI T 249 Carbohydrate

Standard:  

TAPPI

Method:

TAPPI T 249

Title:

Carbohydrate composition of extractive-free wood and wood pulp by gas-liquid chromatography

Scope

TAPPI T 249 is used to determine the five principal monosaccharides which define the carbohydrate composition of wood and wood pulp. The constituents determined quantitatively and on an absolute basis are glucan, mannan, arabinan, xylan and galactan. Concentrations of the individual components as low as 0.1% can be determined. The method is applicable to extractive-free wood as well as to wood pulp.

Summary

Samples are hydrolyzed with sulfuric acid using a two-step technique. A portion of the hydrolyzate is neutralized, and the sugars are reduced to the alditols with sodium borohydride. The alditols are acetylated with acetic anhydride and sulfuric acid, and the alditol acetates are precipitated in ice water and extracted with methylene chloride for injection into the gas chromatograph.

Significance

The carbohydrate composition of a pulp is important in determining its response to processing conditions and the development of physical properties. In addition, the various carbohydrate constituents in wood have different sensitivities to pulping chemicals, and this affects pulp yield and quality. While relative ratios of the monosaccharide constituents may be satisfactory for characterization of dissolving pulps, it is desirable to obtain absolute values for paper grade pulps due to their more complex composition.

The reaction conditions employed in the hydrolysis and derivatization procedures have been selected to minimize losses of the monosaccharides; however, it is known that the losses do occur. These are accounted for by subjecting the monosaccharides to these reaction conditions in the calibration step and by use of an internal standard.

Samples

This test is performed in duplicate, 5 grams of dried material is recommended. A minimum of two samples submitted at the same time is required.

 

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