Stacking and separation of coproporphyrin isomers by acetonitrile-salt mixtures in micellar electrokinetic chromatography

Terence S.K. So, Li Jia, Carmen W K HUIE*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

21 Citations (Scopus)


The effectiveness of the addition of salt and acetonitrile in the sample matrix to induce narrowing of the analyte zones is demonstrated for the first time in micellar electrokinetic chromatography (MEKC). Using coproporphyrin (CP) I and III isomers as test compounds, the use of sodium cholate (SC) as the micelle in the separation buffer and a high concentration of sodium chloride in the aqueous sample solution (without the presence of an organic solvent) were found to provide enhancement in peak heights for both CP I and III, but yielded very poor resolution of these two positional isomers at sample size of 10% capillary volume or larger. With the addition of acetonitrile as the organic solvent in the aqueous sample solution (acetonitrile-salt mixtures), baseline/partial resolution of CP I and III was obtained even at large injection volumes, along with significant increase in peak heights for both isomers. Possible mechanisms responsible for the narrowing of analyte zones are briefly discussed. The effects of experimental parameters, such as concentrations of salt and acetonitrile, on peak heights and resolution of the test compounds were studied. Importantly, the usefulness of the present method was demonstrated for the MEKC determination of endogenous CP I and III present in normal urine samples with good separation and detection performances.

Original languageEnglish
Pages (from-to)2159-2166
Number of pages8
Issue number11
Publication statusPublished - 2001

Scopus Subject Areas

  • Analytical Chemistry
  • Biochemistry
  • Clinical Biochemistry

User-Defined Keywords

  • Acetonitrile-salt mixtures
  • Coproporphyrin isomers
  • Micellar electrokinetic chromatography
  • Stacking


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