Behavior of cation-exchange materials in capillary electrochromatography

Area of Science:

• Analytical Chemistry
• Separation Science

Background:

• Capillary electrochromatography (CEC) and capillary electrophoresis (CE) are powerful separation techniques.
• Strong cation-exchange (SCX) materials, like propanesulfonic acid, are used for specialized separations.

Purpose of the Study:

• To investigate the behavior of SCX material in CE and CEC.
• To evaluate the stability and performance of SCX coatings and packings under various conditions.

Main Methods:

• Studied SCX material in coated and packed capillaries using CE and CEC.
• Varied mobile phase parameters: pH, ionic strength, and acetonitrile content.
• Compared SCX with C(18) packing materials.

Main Results:

• SCX-coated capillaries showed stable electroosmotic flow (EOF) in aqueous electrolytes (pH 3.6-10.5).
• SCX coating stability was questionable in 80% acetonitrile, performing similarly to untreated silica.
• SCX columns exhibited anomalous EOF behavior with decreasing ionic strength and increasing organic content compared to C(18) and open capillaries.

Conclusions:

• SCX material's performance in CEC is highly dependent on mobile phase composition, particularly organic content.
• The stability of SCX coatings in organic-rich mobile phases needs further investigation.
• Anomalous EOF in SCX columns suggests complex interactions not fully explained by standard models.