Systematic Approach to Links between Separations in MEKC and Reversed-Phase HPLC

Area of Science:

• Analytical Chemistry
• Separation Science

Background:

• Micellar electrokinetic chromatography (MEKC) and reversed-phase high-performance liquid chromatography (RP-HPLC) are separation techniques.
• Both methods rely on partitioning analytes between aqueous and alkyl phases.

Purpose of the Study:

• To compare retention factors and partition coefficients in MEKC and RP-HPLC.
• To establish quantitative links between these chromatographic techniques and octanol-water partitioning.

Main Methods:

• Utilized nonporous silica with low carbon loading for RP-HPLC to enable identical mobile phase conditions.
• Employed SDS (C12) micellar pseudostationary phase in MEKC and ODS 2 (C18) stationary phase in RP-HPLC.
• Analyzed alkylbenzenes and substituted phenols.

Main Results:

• The ratio of analyte retention factors (k(MEKC):k(HPLC)) equaled the ratio of phase ratios (β(MEKC):β(HPLC)).
• Partition coefficients (P) were found to be similar in both MEKC and RP-HPLC, indicating dominant hydrophobic interactions.
• Quantitative relationships were established between MEKC, RP-HPLC, and octanol-water partition coefficients (K(ow)).

Conclusions:

• Retention information is transferable between MEKC and RP-HPLC when phase ratios are known.
• Hydrophobic interactions are the primary drivers of retention in both separation modes.
• Acetonitrile had a more pronounced effect on RP-HPLC retention than MEKC retention.