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Chromatographia

, Volume 53, Issue 3–4, pp 190–196 | Cite as

Sensitivity enhancement in capillary electrochromatography by on-column preconcentration

  • M. J. Hilhorst
  • G. W. Somsen
  • G. J. de Jong
Originals Electrophoresis

Summary

The potential of on-column preconcentration in capillary electrochromatography (CEC) to improve the detection limit was investigated. Two test mixtures containing a pharmaceutically relevant steroid (Desogestrel or Tibolon) together with several structurally related compounds were used for evaluation. For both test mixtures, the mobile phase composition was optimised resulting in a baseline separation of all components and plate numbers of up to 1.2·105 plates m−1 within 15 min. An equation was derived which describes the obtainable gain in injection time as function of the analyte retention factor in the mobile phase and in the injection solvent. The proposed model accounts for the focussing of the analytes due to both the retention during injection and the step-gradient during elution. For the experimental study, the least hydrophobic component of the Desogestrel mixture was used. When the mobile phase was used as injection solvent, a considerable decrease in plate number was observed when the injection time exceeded 5 s. By dissolving the analyte in a less-eluting solvent, injection times could be increased up to 60 s without causing significant extra band broadening. Two mixtures containing a relatively high amount of Desogestrel or Tibolon, and the related components at the 0.1% level were analysed to study the potential of the system for impurity profiling. With the mobile phase as injection solvent, the low level components could hardly be detected. By applying large volume injection from a less-eluting injection solvent, a gain in sensitivity of a factor of 7–9 was achieved.

Key Words

Capillary electrochromatography On-column preconcentration Sensitivity enhancement Desogestrel Tibolon 

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Copyright information

© Friedr. Vieweg & Sohn Verlagsgesellschaft mbH 2001

Authors and Affiliations

  • M. J. Hilhorst
    • 1
  • G. W. Somsen
    • 1
  • G. J. de Jong
    • 1
  1. 1.Department of Pharmaceutical AnalysisUniversity Centre for PharmacyGroningenThe Netherlands

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