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Capillary-electrochromatographic separations with copolymeric reversed-stationary phase and ion-exchanger-packed
1University of Iowa, Department of Chemistry, Iowa City 52242, USA.
Journal of Chromatography. A
|July 17, 2001
Summary
Polystyrene-divinylbenzene (PS-DVB) reversed-phase adsorbent (PRP-1) effectively separates pharmaceutical analytes in capillary electrochromatography (CEC). This stable stationary phase offers tunable electroosmotic flow (EOF) and retention for diverse compounds.
Area of Science:
- Analytical Chemistry
- Separation Science
- Chromatography
Background:
- Capillary electrochromatography (CEC) is a powerful separation technique.
- Polystyrene-divinylbenzene (PS-DVB) based stationary phases offer unique properties compared to silica-based materials.
- Optimizing stationary phases is crucial for separating complex pharmaceutical analytes.
Purpose of the Study:
- To evaluate macroporous, spherical, 7 micrometer, polystyrene-divinylbenzene (PS-DVB) reversed-phase adsorbent (PRP-1) as a stationary phase for CEC.
- To investigate the impact of various parameters on electroosmotic flow (EOF) and analyte retention.
- To demonstrate the separation of diverse pharmaceutical analytes using PRP-1 packed capillaries.
Main Methods:
- Capillary electrochromatography (CEC) using a PRP-1 packed capillary.
- Systematic variation of buffer pH, acetonitrile concentration, applied potential, and stationary phase properties.
- Analysis of neutral, acidic, and basic pharmaceutical compounds including steroids, purines, pyrimidines, fatty acids, and sulfa derivatives.
Main Results:
- PRP-1 exhibits stable and high electroosmotic flow (EOF) across a wide pH range (2-10), superior to silica-based C18 on the acidic side.
- EOF is influenced by buffer acetonitrile concentration and applied potential.
- Analyte retention is directly correlated with hydrophobicity and inversely correlated with buffer acetonitrile concentration.
- Increased ion-exchange capacity on PS-DVB enhances EOF and reduces analyte retention.
- High separation efficiencies (approx. 6 x 10^4 plates/m) were achieved for various pharmaceutical compounds.
Conclusions:
- PRP-1 is a robust and versatile stationary phase for CEC of pharmaceutical compounds.
- Its stability in acidic environments allows for separations of acidic and basic analytes.
- PRP-1 offers tunable separation mechanisms through control of EOF and analyte partitioning.