The fallacy of using solvent extraction for the study of metal/ligand complexation in mixed solvent systems

  • Robert Lusk
  • Ashley Rojas
  • Nathalie A. WallEmail author


Metal complexes can be identified by ion mobility mass spectrometry, often using mixed aqueous solvents, which improve the electrospray ionization process but induce significant changes in thermodynamic values associated with metals and ligands. This work demonstrates that the addition of 10% acetonitrile and 1.0% dimethyl sulfoxide leads to an increased autoprotolysis constant, does not influence the nitrilotriacetic acid pKa values, but decreases europium extraction in a solvent extraction system. This work shows the inability to quantify the stability constant of Eu/NTA complex in mixed solvent using a solvent extraction technique, as polar solvents are dissolved in the dodecane organic phase.


Europium Nitrilotriacetic acid Autoprotolysis Solvent extraction Mixed solvents 



This work was supported by the DTRA Basic Research Program (Grant No. HDTRA1-14-1-0023).


  1. 1.
    Davis AL, Clowers BH (2018) Stabilization of gas-phase uranyl complexes enables rapid speciation using electrospray ionization and ion mobility-mass spectrometry. Talanta 176:140–150CrossRefGoogle Scholar
  2. 2.
    Pasilis SP, Pemberton JE (2003) Speciation and coordination chemistry of uranyl(VI)-citrate complexes in aqueous solution. Inorg Chem 42(21):6793–6800CrossRefGoogle Scholar
  3. 3.
    Xiao C-L, Wang C-Z, Mei L, Zhang X-R, Wall N, Zhao Y-L, Chai Z-F, Shi W-Q (2015) Europium, uranyl, and thorium-phenanthroline amide complexes in acetonitrile solution: an ESI-MS and DFT combined investigation. Dalton Trans 44(32):14376–14387CrossRefGoogle Scholar
  4. 4.
    Felmy HM, Bennett KT, Clark SB (2017) The impact of mixed solvents on the complexation thermodynamics of Eu(III) by simple carboxylate and amino carboxylate ligands. J Chem Thermodyn 114:83–92CrossRefGoogle Scholar
  5. 5.
    Bremer A, Mullich U, Geist A, Panak PJ (2015) Influence of the solvent on the complexation of Cm(III) and Eu(III) with nPr-BTP studied by time-resolved laser fluorescence spectroscopy. New J Chem 39(2):1330–1338CrossRefGoogle Scholar
  6. 6.
    Gergely A, Kiss T (1977) Thermodynamic study of copper(II) and nickel(II) complexes of alanine in mixed-solvents. J Inorg Nucl Chem 39(1):109–114CrossRefGoogle Scholar
  7. 7.
    Kole N, Chaudhury AK (1981) Effect of different solvent characteristics on the proton-ligand and Cu2 + -ligand equilibrium and formation-constants of acetyl acetone in various mixed aqueous solvents. J Inorg Nucl Chem 43(10):2471–2480CrossRefGoogle Scholar
  8. 8.
    Xue Y, Traina SJ, Hille R (1996) Stability of metal-organic complexes in acetone- and methanol-water mixtures. Environ Sci Technol 30(11):3177–3183CrossRefGoogle Scholar
  9. 9.
    Mui K-K, McBryde WAE, Nieboer E (1974) Stability of some metal complexes in mixed solvents. Can J Chem 52(10):1821–1833CrossRefGoogle Scholar
  10. 10.
    Gritmon TF, Goedken MP, Choppin GR (1977) The complexation of lanthanides by aminocarboxylate ligands. I. Stability constants. J Inorg Nucl Chem 39(11):2021–2023CrossRefGoogle Scholar
  11. 11.
    Choppin GR, Goedken MP, Gritmon TF (1977) The complexation of lanthanides by aminocarboxylate ligands. II. Thermodynamic parameters. J Inorg Nucl Chem 39(11):2025–2030CrossRefGoogle Scholar
  12. 12.
    Toste AP (1999) Detailed study of the γ-radiolysis of nitrilotriacetic acid in a simulated, mixed nuclear waste. J Radioanal Nucl Chem 239(3):433–439CrossRefGoogle Scholar
  13. 13.
    Klochkov EP, Risovanyi VD, Vaneev VD, Dorofeev AN (2002) Radiation characteristics of europium-containing control rods in a SM-2 reactor after long-term operation. At Energy 93(2):656–660CrossRefGoogle Scholar
  14. 14.
    Klochkov EPR, V.D. (1999) Utilization of europium-containing control rods by development of gamma-europium sources. In: Analysis of risks associated with nuclear submarine decommissioning, dismantling and disposal. SpringerGoogle Scholar
  15. 15.
    Rossotti FJ, Rossotti H (1965) Potentiometric titrations using gran plots—a textbook omission. J Chem Educ 42(7):375CrossRefGoogle Scholar
  16. 16.
    Gans P, O’Sullivan B (2000) GLEE, a new computer program for glass electrode calibration. Talanta 51(1):33–37CrossRefGoogle Scholar
  17. 17.
    Hepler LG, Woolley EM, Hurkot DG (1970) Ionization constants for water in aqueous organic mixtures. J Phys Chem 74(22):3908–3913CrossRefGoogle Scholar
  18. 18.
    Gonzalez AG, Herrador MA (1997) Ionization constants of water insoluble arylpropionic acids in aqueous N, N’-dimethylformamide mixtures from potentiometric pH-titrations. Anal Chim Acta 356(2–3):253–258CrossRefGoogle Scholar
  19. 19.
    Farajtabar A, Gharib Farrokh (2009) Autoprotolysis constants determination of water-methanol mixtures and solvent effect. J Taibah Univ Sci 2:7–13CrossRefGoogle Scholar
  20. 20.
    Alderighi L, Gans P, Ienco A, Peters D, Sabatini A, Vacca A (1999) Hyperquad simulation and speciation (HySS): a utility program for the investigation of equilibria involving soluble and partially soluble species. Coord Chem Rev 184:311–318CrossRefGoogle Scholar
  21. 21.
    Pierce TB, Peck PF (1963) The extraction of the lanthanide elements from perchloric acid by di-(2-ethylhexyl) hydrogen phosphate. Analyst 88(1044):217–221CrossRefGoogle Scholar
  22. 22.
    Rumble J (2019) CRC handbook of chemistry and physics, 100th edn. CRC Press, Boca RatonGoogle Scholar

Copyright information

© Akadémiai Kiadó, Budapest, Hungary 2019

Authors and Affiliations

  1. 1.Department of ChemistryWashington State UniversityPullmanUSA

Personalised recommendations