Silanizing agent for semipermanent wall coating in micellar electrokinetic capillary chromatography

Area of Science:

• Analytical Chemistry
• Separation Science

Background:

• Micellar electrokinetic capillary chromatography (MEKC) is a powerful separation technique.
• Fused-silica capillaries often require surface modification to optimize performance.
• Stable capillary coatings are crucial for reproducible electrokinetic separations.

Purpose of the Study:

• To investigate chloro(dodecyl)dimethylsilane (CDDS) as a semipermanent capillary coating for MEKC.
• To evaluate the stability and performance of the CDDS coating.
• To assess the impact of the CDDS coating on electroosmotic flow (EOF) and separation reproducibility.

Main Methods:

• Application of chloro(dodecyl)dimethylsilane (CDDS) as a silanizing agent to fused-silica capillaries.
• Formation of a stable coating via covalent bonding with silanol groups.
• Utilizing sodium dodecyl sulfate (SDS) as an anionic surfactant in the running buffer.
• Analysis of amino acids using MEKC with optimized buffer conditions (60mM sodium tetraborate, 12 mM SDS at pH 9.9, 20 kV, 25°C).

Main Results:

• The CDDS coating demonstrated high stability, remaining effective for over 100 minutes after rinsing.
• The CDDS coating facilitated the formation of an SDS layer, significantly increasing EOF.
• EOF increased from 4.34 x 10⁻⁴ cm²V⁻¹s⁻¹ to 7.02 x 10⁻⁴ cm²V⁻¹s⁻¹ compared to no-coating methods.
• Excellent migration time reproducibility was achieved ( <0.97% R.S.D. run-to-run, <1.56% R.S.D. day-to-day).

Conclusions:

• Chloro(dodecyl)dimethylsilane (CDDS) provides a robust and effective semipermanent coating for MEKC.
• The CDDS coating enhances EOF and improves the reproducibility of amino acid separations.
• This silanization method offers a valuable approach for optimizing MEKC performance.