Journal of Analytical Chemistry

, Volume 70, Issue 10, pp 1267–1270 | Cite as

Potentiometric determination of trace acidic impurities in lactide



A method for the determination of trace acidic impurities in lactide using potentiometric titration in a non-aqueous medium is described. Lactic acid and its oligomers residue in lactide used for polymerization has a strong influence on the size and molar mass distribution of the resulting polylactide. In the case of the polymers of high quality, lactide with a content of free acids at the level of individual millimoles per kilogram is used. The described method demonstrates a new way for detecting the end point with the potentiometric electrode used for measuring in a non-aqueous environment. The effectiveness of the method has been verified for the methanolic solvent (known from the literature) and acetonitrile (not used previously). Concentration of the titrant and size of the sample were optimized. The determined content of acidic impurities in high-quality lactide determined by direct titration and the standard addition method was consistent with manufacturer’s specifications.


lactide vlactic acid acid impurities potentiometric titration 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Vink, E.T.H., Rábago, K.R., Glassner, D.A., and Gruber, P.R., Polym. Degrad. Stab., 2003, vol. 80, p. 403.CrossRefGoogle Scholar
  2. 2.
    Auras, R., Harte, B., and Selke, S., Macromol. Biosci., 2004, vol. 4, p. 835.CrossRefGoogle Scholar
  3. 3.
    Jamshidian, M., Tehrany, E.A., Imran, M., Jacquot, M., and Desobry, S., Compr. Rev. Food Sci. F., 2010, vol. 9, p. 552.CrossRefGoogle Scholar
  4. 4.
    Inkinen, S., Hakkarainen, M., Albertsson, A.-Ch., and Sodergard, A., Biomacromolecules, 2011, vol. 12, p. 523.CrossRefGoogle Scholar
  5. 5.
    Zhang, H.-P., Ruan, J.-M., Zhou, Z.-Ch., and Li, Y.-J., J. Cent. South Univ. Technol. (Engl. Ed.), 2005, vol. 12, no. 3, p. 246.CrossRefGoogle Scholar
  6. 6.
    Tsukegi, T., Motoyama, T., Shirai, Y., Nishida, H., and Endo, T., Polym. Degrad. Stab., 2007, p. 552.Google Scholar
  7. 7.
    Groot, W., van Krieken, J., Sliekersl, O., and de Vos, S., in Poly(Lactic Acid): Synthesis, Structures, Properties, Processing, and Applications, Auras, R., Loong-Tak, L., Selkeand, S.E.M., and Tsuji, H., Eds., Gorinchem: Wiley, 2010, ch. 1.Google Scholar
  8. 8.
    Jacobsena, S., Fritza, H.-G., Degeeb, P., Duboisb, P., and Jeromec, R., Ind. Crops Prod., 2000, vol. 11, p. 265.CrossRefGoogle Scholar
  9. 9.
    Zhang, X., MacDonald, D.A., Goosen, M.F.A., and McAuley, K.B., J. Polym. Sci., Part A: Polym. Chem., 1994, vol. 32, p. 2965.CrossRefGoogle Scholar
  10. 10.
    Garlotta, D., J. Polym. Environ., 2002, vol. 9, p. 63.CrossRefGoogle Scholar
  11. 11.
    Witzke, D.R., Narayan, R., and Kolstad, J.J., Macromolecules, 1997, vol. 30, p. 7075.CrossRefGoogle Scholar
  12. 12.
    Nieuwenhuis, J. and Mol, A.C., US Patent 5053485, 1991.Google Scholar
  13. 13.
    Combined electrode ERH NS: User Manual. Accessed March 31, 2015.Google Scholar
  14. 14.
    Manual User Titrator Metrohm, Metrodata TiNet 2.4 6.6012.X40: Accessed March 31, 2015.Google Scholar

Copyright information

© Pleiades Publishing, Ltd. 2015

Authors and Affiliations

  1. 1.Laboratory of Technological Processes, Faculty of ChemistryWarsaw University of TechnologyWarsawPoland

Personalised recommendations