Institute of Physical and Theoretical Chemistry

Basic research on separation principles and mechanisms

The analytes’ physicochemical characteristics largely determine the choice of the separation technique. Beside classical chromatography, our group uses nearly all electromigrative separation techniques including capillary electrophoresis, micellar electrokinetic chromatography, isoelectric focussing, isotachophoresis, non-aqueous capillary electrophoresis and sieze-sieving electrophoresis. These separation modes are based on different separation principles, not all of which are fully understood, showing the necessity of further basic research. The same holds true for preconcentration techniques, which help to improve detection limits. Their underlying effects are also relevant for the optimization of the sample transfer in multidimensional separation techniques.

For non-aqueous capillary electrophoresis we were able to show that ion pair formation and coupled equilibria dominate separations in a non-aqueous environment. For isotachophoresis, the understanding of ion-pairing principles allowed implementing weak bases into the ITP stack for the first time, which allowed the simultaneous online preconcentration of all amino acids in a single run.

Other projects are related to protein isoform separation with isoelectric focusing, including the possibility to focus analytes at specific segments of the separation capillary which is required for heart-cut sample transfer in multidimensional electromigrative separation techniques. Our experimental work on these fields is accompanied via computational simulations by our cooperation partners to enhance the understanding of the fundamental effects which affect analyte separation in the two-dimensional setup. Furthermore, the use of Design-of-Experiments strategies proved essential.

Cooperations:

  • Pablo Kler, Centro de Investigación de Métodos Computacionales (CIMEC), Universidad Nacional del Litoral (UNL), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Santa Fe, Argentina
  • Marián Masár, Milan Hutta, Department of Analytical Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina CH-2, 842 15, Bratislava, Slowakei

Publications:

  1. Non-aqueous electrolytes for isotachophoresis of weak bases and its application to the comprehensive preconcentration of the 20 proteinogenic amino acids in column-coupling ITP/CE-MS
    P. A. Kler, C. Huhn, Anal. Bioanal. Chem. 2014, 28, 7163-7174

  2. Advantages and limitations of a new cationic coating inducing a slow electroosmotic flow for CE-MS peptide analysis: a comparative study with commercial coatings
    M. Pattky, C. Huhn*, Anal. Bioanal. Chem. 2013, 405, 225-237

  3. Desulfurized fuels from Athabasca bitumen and their polycyclic aromatic sulfur heterocycles. Analysis based on capillary electrophoresis coupled with TOF MS
    T. Nolte, T. N. Posch, C. Huhn, J. T. Andersson, Energy Fuels 2013, 27, 97-107
  4. Non-aqueous capillary electrophoresis – mass spectrometry: A versatile, straightforward tool for the analysis of alkaloids from psychoactive plant extracts
    T. N. Posch, N. Martin, M. Pütz, C. Huhn, Electrophoresis 2012, 33, 1557-1566
  5. Implementation of a design of experiments to study the influence of the background electrolyte on separation and detection in non-aqueous capillary electrophoresis – mass spectrometry
    T. N. Posch, A. Müller, W. Schulz, M. Pütz, C. Huhn, Electrophoresis 2012, 33, 583-598
  6. Processes involved in sweeping under inhomogeneous electric field conditions as sample enrichment procedure in micellar electrokinetic chromatography
    M. El-Awady, C. Huhn, U. Pyell, J. Chromatogr. A 2012, 1264, 124-136
  7. Diffusion as a major source of band-broadening in field-amplified sample stacking under negligible electroosmotic flow velocity conditions
    C. Huhn, U. Pyell, J. Chromatogr. A 2010, 1217, 4476-4486
  8. Calibration-free concentration determination of charged colloidal nanoparticles and determination of effective charges by capillary isotachophoresis
    U. Pyell, W. Bücking, C. Huhn, B. Herrmann, A. Merkoulov, J. Mannhardt, H. Jungclas, T. Nann, Anal. Bioanal. Chem. 2009, 395, 1681-1691
  9. Separation of very hydrophobic analytes by micellar electrokinetic chromatography IV. Modelling of the effec­tive electrophoretic mobility from carbon number equivalents and octanol-water partition coefficients
    C. Huhn, U. Pyell, J. Chromatogr. A 2008, 1198-1199, 208-214
  10. Separation of very hydrophobic analytes by micellar electrokinetic chromatography III. Charac­terization and optimization of the separation electrolyte using carbon numbers
    C. Huhn, M. Pütz, U. Pyell, Electrophoresis 2008, 29, 783-795
  11. Separation of very hydrophobic analytes by micellar electrokinetic chromatography II. Carbon number equiva­lents as analyte descriptors – influence of the composition of the separation elec­trolyte
    C. Huhn, M. Pütz, U. Pyell, Electrophoresis 2008, 29, 567-575
  12. Separation of very hydrophobic analytes by micellar electrokinetic chromatography I. Optimi­zation of the composi­tion of the sample solution for the determination of the aromatic ingredients of sassafras and other es­sential oils of forensic interest
    C. Huhn, M. Pütz, I. Holthausen, U. Pyell, Electrophoresis 2008, 29, 526-537
  13. Chirale Analytik mit Kapillarelektrophorese
    C. Huhn, M. Bauerfeind, GIT Spezial – Separation 1/2010