Critical comparison and validation of methods for determination of anionic groups in pulp fibres

P Fardim*, B Holmbom, A Ivaska, J Karhu, G Mortha, J Laine

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review


Anionic or acidic groups in pulp fibres are important for many interactions in pulping and papermaking. The total amount of anionic groups can be determined by acid-base titration, as well as different sorption and ion-exchange techniques. In this study, different methods for determination of total anionic groups were compared on a broad selection of pulps. Conductometric titration with NaOH and methylene blue sorption gave very similar results on all pulps, and both methods had a good repeatability. The methylene blue technique is especially attractive because of its simplicity. Polyelectrolyte adsorption with polybrene generally gave higher readings, was less repeatable, and was also a very laborious method. Uronic acids, including hexenuronic acid, determined by enzymatic hydrolysis and HPLC (High Pressure Liquid Chromatography), represented only 20-60% of the total anionic groups in the kraft pulps. Uronic acids analysed by acid methanolysis and GC (Gas Chromatography) usually represents 70-100% of the anionic groups in mechanical pulps.

Original languageEnglish
Pages (from-to)346-351
Number of pages6
JournalNordic Pulp & Paper Research Journal
Issue number3
Publication statusPublished - 2002
MoE publication typeA1 Journal article-refereed


  • uronic acids
  • carboxyl groups
  • sulphonic acid groups
  • acid-base titration
  • methylene blue sorption
  • polyeletrolyte adsorption
  • ion exchange

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