Use of Capillary Zone Electrophoresis and Micellar Electrokinetic Chromatography for Separations of Anthraquinone Derivatives

Abstract

The behavior of seven hydroxy anthraquinone derivatives was studied by capillary zone electrophoresis and micellar electrokinetic chromatography. The effects of buffer pH (6.5–10.8) and sodium dodecyl sulfate concentration (10–20 mmol L⁻¹) on the effective mobilities of the analytes and their separation were tested. A comparison of the two optimized separation systems showed that micellar electrokinetic chromatography was superior as it permits separation of all the seven analytes within 15 min, using 15 mmol L⁻¹ sodium dodecyl sulfate in 10 mmol L⁻¹ tetraborate buffer, pH 8.5, at a voltage of 20 kV. The calibration curves were linear in the concentration range from 5.0 · 10⁻⁷ to 5.0 · 10⁻⁴ mol L⁻¹ for most of the analytes, at a detection wavelength of 254 nm. LOD and LOQ values of the analytes were in the ranges of 2.10 · 10⁻⁷–1.28 · 10⁻⁶ mol L⁻¹and 6.99 · 10⁻⁷–4.25 · 10⁻⁶ mol L⁻¹, respectively. The proposed separation conditions were applied to determination of 1,2-dihydroxy anthraquinone (alizarin) and 1,2,4-trihydroxy anthraquinone (purpurin) in Rubia tinctorum aglycone and of the recently described 1-acetyl-2,4,5,7-tetrahydroxy-9,10-anthraquinone and 1-acetyl-2,4,5,7,8-pentahydroxy-9,10-anthraquinone in the mycelium of fungi Geosmithia lavendula.

Keywords:

• CZE
• Hydroxy anthraquinones
• MEKC
• Quantitation
• Real sample analyses
• Separation

Acknowledgments

The authors are grateful to the Ministry of Education, Youth and Sports of the Czech Republic, projects MSM 0021620857 and RP 14/63, for financial and material support. ES also thanks the Grant Agency of the Charles University (Projects 69807 and SVV 261204) for financial support. ET and JL acknowledge CEEPUS project CII-HU-0010-01-1011.

Notes

BGE: 10 mmol L⁻¹ phosphate buffer or 10 mmol L⁻¹ tetraborate buffer.

BGE: 10 mmol L⁻¹ phosphate buffer (pH 6.5–7.5) or 10 mmol L⁻¹ tetraborate buffer (pH 8.5–10.8).

Limits of detection (LOD) and limits of quantification (LOQ) of the analytes calculated from the dependencies of peak height versus analyte concentration. BGE: 10 mmol L⁻¹ tetraborate buffer pH 8.5 with 15 mmol L⁻¹ SDS, hydrodynamic injection 20 mbar for 5 s, separation voltage 20 kV, detection 254 nm.

n – number of measurements.

BGE: 10 mmol L⁻¹ tetraborate buffer, pH 8.5, with 15 mmol L⁻¹ SDS, hydrodynamic injection 20 mbar for 5 s, separation voltage 20 kV, detection 254 nm.