A novel normalized retention factor in micellar electrokinetic chromatography

Area of Science:

• Analytical Chemistry
• Separation Science

Background:

• Micellar electrokinetic capillary chromatography (MEKC) is a powerful separation technique.
• Accurate characterization of analyte hydrophobicity is crucial for understanding MEKC behavior.
• Existing hydrophobicity parameters may not fully capture the complexities of MEKC systems.

Purpose of the Study:

• To evaluate the characteristic properties and applicability of a new expression, k'' = (t(m)-t(o))/(t(mc)-t(o)), for analyte hydrophobicity in MEKC.
• To compare the performance of k'' with the previously established Terabe expression, k' = (t(m)-t(o))/t(o)(1-t(m)/t(mc)).
• To validate the utility of k'' using experimental data from various compound classes.

Main Methods:

• Theoretical calculations, including curve shape analysis, were employed to assess the properties of the k'' expression.
• Experimental validation was performed using homolog series of alkylbenzenes, alkylphenones, and protected peptides.
• Migration times, k', k'' values, and software-calculated hydrophobicity data were systematically collected and analyzed.

Main Results:

• Theoretical analysis confirmed that the properties of k'' are consistent with MEKC system behavior.
• Experimental data supported the advantageous application of k'' for characterizing analyte hydrophobicity.
• The normalized nature of k'' facilitated strong correlations between migration time, software-calculated hydrophobicity, and k'' values.
• k'' provided a more realistic estimation of hydrophobicity differences compared to k'.

Conclusions:

• The k'' expression is a valuable and accurate parameter for characterizing analyte hydrophobicity in MEKC.
• Hydrophobicity data derived from k'' align well with migration times and chemical structure expectations.
• The k'' parameter offers improved insights into analyte behavior within MEKC systems.