Uronic acids analytical determinations

Blumenkrantz, N., Asboe-Hansen, G. (1973). New method for quantitative determination of uronic acids. Analytical Biochemistry, 54,484—489. 

Blumenkrantz, N., and G. Asboe-Hansen New Method for Quantitative Determination of Uronic Acids. Analyt. Biochem. 54, 484 (1973). 

Uronic acid content was determined as anhydro-uronic acid (AUA) by the automated colorimetric /n-hydroxydiphenyl assay [2,3,6] using an auto-analyser (Skalar Analytical BV, Breda, The Netherlands). Corrections were made for interference by neutral sugars present in the sample. 

The analytical determinations most often made on a polyuronide before it is hydrolyzed are those for uronic acid, pentosan, methyl-pentosan, methoxyl and ash. The percentage of hexosan is usually estimated by difference. When the polyuronide has been obtained as a free acid it can in many cases be titrated with a base. Such metals as sodium, potassium, magnesium, calcium and iron often occur and especially so in plant gums and mucilages. 

The new MALDI-MS based analytical procedures described in this chapter have been employed successfully for (i) determining the accurate molar mass and molar mass distribution for different types of xylans and glucomannans, (ii) characterizing the distribution of uronic acid residues in hard- and softwood xylans and (iii) determining the content and distribution of 0-acetyl substituents in xylans and glucomannans. 

In addition to the total carbohydrate assay for xanthan using the Dubois method, there are specific analytical methods that may be applied to determine how much of a specific group is present. For example, specific micromethods were applied by Nisbet et al (1982) to assay for 0-acetyl groups, pyruvate ketals and uronic acids. Further discussion of such methods is beyond the scope of this work. 

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