Assessment of polyelectrolyte coating stability under dynamic buffer conditions in CE

Area of Science:

• Analytical Chemistry
• Separation Science
• Materials Science

Background:

• Dynamic buffer conditions are common in electrophoretically driven separations.
• Polyelectrolyte multilayer (PEM) coatings offer stability and ease of application in capillary electrophoresis (CE).

Purpose of the Study:

• To measure the effect of dynamic buffer pH changes on electroosmotic flow (EOF) in real-time.
• To evaluate the stability and EOF response of PEMs with varying polyelectrolyte types and thicknesses.

Main Methods:

• PEMs were constructed using strong (e.g., poly(diallyldimethylammonium) chloride) and weak (e.g., poly(allylamine)) polyelectrolytes.
• EOF was monitored in real-time (every 2 s) while buffer pH was systematically decreased from 7.1 to 5.1.
• Coatings of varying thicknesses (3-16 layers) were tested.

Main Results:

• Strong polyelectrolytes showed minimal EOF change (<1%) with pH variation.
• Weak polyelectrolytes exhibited substantial (>10%) and sometimes irreversible EOF changes.
• Thicker coatings were less stable and more prone to degradation under pH stress.

Conclusions:

• Thin coatings of strong polyelectrolytes provide the most stable performance under dynamic buffer pH conditions.
• The choice of polyelectrolyte type is critical for managing EOF stability in CE.
• PEM coatings offer tunable properties for electrophoretic separations.