Electrophoretic separations in poly(dimethylsiloxane) microchips using a mixture of ionic and zwitterionic...

Area of Science:

• Analytical Chemistry
• Materials Science
• Biochemistry

Background:

• Poly(dimethylsiloxane) (PDMS) microfluidic devices are widely used in chemical analysis.
• Controlling electroosmotic flow (EOF) is crucial for optimizing separations in microchips.
• Surfactants are commonly employed to modify EOF, but their behavior can be complex.

Purpose of the Study:

• To investigate the effect of mixed ionic and zwitterionic surfactants on EOF in PDMS microchips.
• To evaluate the adsorption/desorption kinetics of these surfactants.
• To demonstrate the application of mixed surfactant systems for the separation and detection of analytes.

Main Methods:

• Systematic study of electroosmotic flow (EOF) with varying concentrations of sodium dodecyl sulfate (SDS) and N-tetradecylammonium-N,N-dimethyl-3-ammonio-1-propanesulfonate (TDAPS).
• Measurement of surfactant adsorption/desorption kinetics.
• Separation and electrochemical detection of model catecholamines and reduced glutathione in complex matrices.

Main Results:

• Single SDS increased EOF, while TDAPS showed concentration-dependent effects.
• Mixed SDS/TDAPS systems allowed tunable EOF across different pH and concentrations.
• TDAPS exhibited slower adsorption/desorption kinetics compared to SDS.
• The mixed surfactant system improved separation resolution and reduced analysis times for target analytes.

Conclusions:

• Mixed ionic and zwitterionic surfactants offer a versatile approach to control EOF in PDMS microchips.
• The tunable nature of the mixed system enhances its applicability for complex analytical challenges.
• This strategy provides a pathway for developing more efficient microfluidic separation and detection systems.