, Volume 22, Issue 1, pp 101–116 | Cite as

General procedure for determining cellulose nanocrystal sulfate half-ester content by conductometric titration

  • Stephanie BeckEmail author
  • Myriam Méthot
  • Jean Bouchard
Original Paper


Charged groups on the surface of cellulose nanocrystals (CNCs) control the colloidal stability and electrostatic and rheological properties of aqueous CNC suspensions, as well as their ability to self-assemble into liquid crystalline structures with unique optical properties. CNCs extracted from wood pulp by sulfuric acid hydrolysis typically contain 200–300 mmol/kg of anionic sulfate half-esters introduced at some of the hydroxyl sites. Two analysis methods to determine CNC surface charge are presented in the published literature: total sulfur content determination by elemental analysis and protonated sulfate half-ester group determination by conductometric titration with sodium hydroxide. The main drawbacks to elemental analysis are the expensive and complicated instrumentation and sample preparation procedures it requires. Conductometric titration is a much simpler method, but requires complete protonation of the CNC samples in order to obtain an accurate value. Unfortunately, significant discrepancies between the sulfate half-ester contents measured with the two techniques are often observed in the literature, particularly with neutralized Na-CNCs. There are specific assumptions and pitfalls inherent to both analysis methods which must be taken into account and reconciled if comparable results are to be achieved by titration and elemental analysis. In particular, sample preparation is crucial to obtaining accurate determinations of sulfate half-ester content by conductometric titration; however, methods differ widely among laboratories and are often not specified in detail, rendering published results meaningless. We have developed a rapid sample preparation protocol which allows quantitative and accurate determination of the sulfate half-ester content of CNCs from various cellulosic feedstocks (for H- and Na-CNCs, in both never-dried and redispersed dried forms) by conductometric titration, yielding results in good agreement with the total sulfur content determined by elemental analysis.


Cellulose nanocrystals Sulfate half-esters Conductometric titration Ion exchange Dialysis Elemental analysis 



The authors thank Alexander Cheng for performing the batch ion-exchange resin treatment experiments; Giuseppa Zambito and Beth Ambayec for performing the ICP-AES analyses; Philippe Bourassa for analysis of the CelluForce CNC sample; Naceur Jemaa, Carole Fraschini and Greg Chauve for insightful suggestions; and the FPInnovations CNC pilot plant team, particularly Bill Reed, for providing the NBSK, NBSS and sisal CNCs and for helpful discussions. We also thank Tiffany Abitbol for valuable discussions. We gratefully acknowledge René Goguen (CelluForce), Christophe Danumah (AITF), Alan Rudie (USFPL), and Bruno Jean (Cermav) for providing CNC samples and for useful information.


  1. Abitbol T, Kloser E, Gray DG (2013) Estimation of the surface sulfur content of cellulose nanocrystals prepared by sulfuric acid hydrolysis. Cellulose 20(2):785–794CrossRefGoogle Scholar
  2. Araki J (2013) Electrostatic or steric?—preparations and characterizations of well-dispersed systems containing rod-like nanowhiskers of crystalline polysaccharides. Soft Matter 9(16):4125–4141CrossRefGoogle Scholar
  3. Araki J, Kuga S (2001) Effect of trace electrolyte on liquid crystal type of cellulose microcrystals. Langmuir 17(15):4493–4496CrossRefGoogle Scholar
  4. Araki J, Wada M, Kuga S, Okano T (1998) Flow properties of microcrystalline cellulose suspension prepared by acid treatment of native cellulose. Colloids Surf A 142(1):75–82CrossRefGoogle Scholar
  5. Araki J, Wada M, Kuga S, Okano T (1999) Influence of surface charge on viscosity behavior of cellulose microcrystal suspension. J Wood Sci 45(3):258–261CrossRefGoogle Scholar
  6. Araki J, Wada M, Kuga S (2001) Steric stabilization of a cellulose microcrystal suspension by poly(ethylene glycol) grafting. Langmuir 17(1):21–27CrossRefGoogle Scholar
  7. Beck S, Bouchard J (2014) Auto-catalyzed acidic desulfation of cellulose nanocrystals. Nord Pulp Pap Res J 29(1):6–14CrossRefGoogle Scholar
  8. Beck S, Bouchard J, Berry R (2011) Controlling the reflection wavelength of iridescent solid films of nanocrystalline cellulose. Biomacromolecules 12(1):167–172CrossRefGoogle Scholar
  9. Beck S, Bouchard J, Berry R (2012) Dispersibility in water of dried nanocrystalline cellulose. Biomacromolecules 13(5):1486–1494CrossRefGoogle Scholar
  10. Beck-Candanedo S, Roman M, Gray DG (2005) Effect of reaction conditions on the properties and behavior of wood cellulose nanocrystal suspensions. Biomacromolecules 6(2):1048–1054CrossRefGoogle Scholar
  11. Bio-Rad Laboratories AG® 501-X8 and Bio-Rex® MSZ 501(D) Mixed Bed Resin Instruction Manual, LIT205 Rev B. Received February 12, 2013Google Scholar
  12. Bio-Rad Technical Support FAQ: Accessed 6 Dec 2013
  13. Brinchi L, Cotana F, Fortunati E, Kenny JM (2013) Production of nanocrystalline cellulose from lignocellulosic biomass: technology and applications. Carbohydr Polym 94(1):154–169CrossRefGoogle Scholar
  14. Camarero Espinosa S, Kuhnt T, Foster EJ, Weder C (2013) Isolation of thermally stable cellulose nanocrystals by phosphoric acid hydrolysis. Biomacromolecules 14(4):1223–1230CrossRefGoogle Scholar
  15. de Dardel F (2013) Ion exchange resin structure. Accessed 28 Nov 2013
  16. Dong XM, Gray DG (1997) Effect of counterions on ordered phase formation in suspensions of charged rodlike cellulose crystallites. Langmuir 13(8):2404–2409CrossRefGoogle Scholar
  17. Dong XM, Kimura T, Revol J-F, Gray DG (1996) Effects of ionic strength on the isotropic-chiral nematic phase transitions of suspensions of cellulose crystallites. Langmuir 12(8):2076–2082CrossRefGoogle Scholar
  18. Dong XM, Revol J-F, Gray DG (1998) Effect of microcrystallite preparation conditions on the formation of colloid crystals of cellulose. Cellulose 5(1):19–32CrossRefGoogle Scholar
  19. DOWEX Ion Exchange Resins Tech Facts Form No. 177-01836-502XQRP: Color Release from Cation Resins. Accessed 6 Dec 2013
  20. DOWEX Ion Exchange Resins Tech Facts Form No. 177-01755-0207: Using Ion Exchange Resin Selectivity Coefficients. Accessed 15 Jan 2014
  21. Gu J, Catchmark JM, Kaiserc EQ, Archibald DD (2013) Quantification of cellulose nanowhiskers sulfate esterification levels. Carbohydr Polym 92(2):1809–1816CrossRefGoogle Scholar
  22. Hamad WY, Hu TQ (2010) Structure–property–process inter-relationships in nanocrystalline cellulose extraction. Can J Chem Eng 88(3):392–402Google Scholar
  23. Hasani M, Cranston ED, Westman G, Gray DG (2008) Cationic surface functionalization of cellulose nanocrystals. Soft Matter 4(11):2238–2244CrossRefGoogle Scholar
  24. Jiang F, Esker AR, Roman M (2010) Acid-catalyzed and solvolytic desulfation of H2SO4–hydrolyzed cellulose nanocrystals. Langmuir 26(23):17919–17925CrossRefGoogle Scholar
  25. Katz S, Beatson RP, Scallan AM (1984) The determination of strong and weak acid groups in sulfite pulps. Svensk Papperstid 87(6):R48–R53Google Scholar
  26. Kaur H (2010) Instrumental methods of chemical analysis. Global Media, MeerutGoogle Scholar
  27. Kloser E, Gray DG (2010) Surface grafting of cellulose nanocrystals with poly(ethylene oxide) in aqueous media. Langmuir 26(16):13450–13456CrossRefGoogle Scholar
  28. Lagerwall JPF, Schütz C, Salajkova M, Noh JH, Park JH, Scalia G, Bergström L (2014) Cellulose nanocrystal-based materials: from liquid crystal self-assembly and glass formation to multifunctional thin films. NPG Asia Mater 6:e80. doi: 10.1038/am.2013.69 CrossRefGoogle Scholar
  29. Leung ACW, Hrapovic S, Lam E, Liu Y, Male KB, Mahmoud KA, Luong JHT (2011) Characteristics and properties of carboxylated cellulose nanocrystals prepared from a novel one-step procedure. Small 7(3):302–305CrossRefGoogle Scholar
  30. Leung CW, Luong JHT, Hrapovic S, Lam E, Liu Y, Male KB, Mahmoud K, Rho D (2012) Cellulose nanocrystals from renewable biomass. U.S. Patent Application US 2012/0244357 A1Google Scholar
  31. Lin N, Huang J, Dufresne A (2012) Preparation, properties and applications of polysaccharide nanocrystals in advanced functional nanomaterials: a review. Nanoscale 4(11):3274–3294CrossRefGoogle Scholar
  32. Marchessault RH, Koch MJ, Yang JT (1961a) Some hydrodynamic properties of ramie crystallites in phosphate buffer. J Colloid Sci 16(4):345–360CrossRefGoogle Scholar
  33. Marchessault RH, Morehead FF, Koch MJ (1961b) Some hydrodynamic properties of neutral suspensions of cellulose crystallites as related to size and shape. J Colloid Sci 16(4):327–344CrossRefGoogle Scholar
  34. Revol J-F, Godbout L, Dong X-M, Gray DG, Chanzy H, Maret G (1994) Chiral nematic suspensions of cellulose crystallites; phase separation and magnetic field orientation. Liq Cryst 16(1):127–134CrossRefGoogle Scholar
  35. Revol J-F, Godbout L, Gray DG (1998) Solid self-assembled films of cellulose with chiral nematic order and optically variable properties. J Pulp Pap Sci 24(5):146–149Google Scholar
  36. Rohm and Haas Company (2008) Amberlite™ MB6113 Industrial Grade Non-Regenerable Mixed Bed Resin. Lenntech Product Information Sheet PDS 333 AGoogle Scholar
  37. Roman M, Winter WT (2004) Effect of sulfate groups from sulfuric acid hydrolysis on the thermal degradation behavior of bacterial cellulose. Biomacromolecules 5(5):1671–1677CrossRefGoogle Scholar
  38. Salajková M, Berglund LA, Zhou Q (2012) Hydrophobic cellulose nanocrystals modified with quaternary ammonium salts. J Mater Chem 22(37):19798–19805CrossRefGoogle Scholar
  39. Samuelson O (1953) Ion exchangers in analytical chemistry. Wiley, New YorkGoogle Scholar
  40. Shafiei-Sabet S, Hamad WY, Hatzikiriakos SG (2012) Rheology of nanocrystalline cellulose aqueous suspensions. Langmuir 28(49):17124–17133CrossRefGoogle Scholar
  41. Shafiei-Sabet S, Hamad WY, Hatzikiriakos SG (2013) Influence of degree of sulfation on the rheology of cellulose nanocrystal suspensions. Rheol Acta 52(8–9):741–751CrossRefGoogle Scholar
  42. Suflet DM, Chitanu GC, Popa VI (2006) Phosphorylation of polysaccharides: new results on synthesis and characterisation of phosphorylated cellulose. React Funct Polym 66(11):1240–1249CrossRefGoogle Scholar
  43. Teixeira EM, de Oliveira CR, Mattoso LHC, Corrêa AC, Paladin PD (2010) Cotton nanofibers obtained by different hydrolytic acid conditions. Polímeros 20(4):264–268CrossRefGoogle Scholar
  44. Wang H, Roman M (2011) Formation and properties of chitosan–cellulose nanocrystal polyelectrolyte–macroion complexes for drug delivery applications. Biomacromolecules 12(5):1585–1593CrossRefGoogle Scholar
  45. Wang N, Ding E, Cheng R (2007) Thermal degradation behaviors of spherical cellulose nanocrystals with sulfate groups. Polymer 48(12):3486–3493CrossRefGoogle Scholar
  46. Winter SS (1956) Ion-exchange separations. J Chem Ed 33(9):473–477CrossRefGoogle Scholar
  47. Wu Q, Meng Y, Wang S, Li Y, Fu S, Ma L, Harper D (2014) Rheological behavior of cellulose nanocrystal suspension: influence of concentration and aspect ratio. J Appl Polym Sci 131(15):40525Google Scholar
  48. Zhong L, Fu S, Peng X, Zhan H, Sun R (2012) Colloidal stability of negatively charged cellulose nanocrystalline in aqueous systems. Carbohydr Polym 90(1):644–649CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media Dordrecht 2014

Authors and Affiliations

  1. 1.Pulp, Paper and Biomaterials DivisionFPInnovationsPointe-ClaireCanada

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