SEPARATION OF HISTORICAL DYES USING CAPILLARY ELECTROPHORESIS WITH LASER-INDUCED FLUORESCENCE DETECTION

Abstract

In this study, the separation properties of alizarin, purpurin, carmin, and morin were explored using capillary electrophoresis (CE). A 30-cm capillary (10 µm i.d.) and an applied voltage of 16–20 kV was used to separate the dyes prior to post-column detection in a sheath flow cuvette using laser-induced fluorescence (LIF). Two lasers were used for excitation: a 488 nm argon ion laser and a 407 nm diode laser (50 mW). Samples were electro-kinetically injected (10 kV for 5 s) into the capillary. Detection limits for alizarin, purpurin, carmine, and morin (n = 3) were determined to be 1.0, 2.1, 3.4, and 0.3 µg L⁻¹, respectively. The extraction of alizarin from two powdered sources of Rubia tinctorum (madder) was also achieved using dimethyl sulfoxide (DMSO) that was heated gently prior to dilution with a 20-mM borate buffer. Concentrations of alizarin in two sources of powdered madder root were found to be 10.2–10.7 mg g⁻¹.

Keywords:

• alizarin
• capillary electrophoresis
• carmine
• dyes
• fluorescence
• morin
• purpurin

ACKNOWLEDGMENT

Funding for this research was provided by the Natural Sciences and Engineering Research Council of Canada (NSERC). The University of Winnipeg is also acknowledged for its support of this research. D. Goltz is an adjunct professor and S. Ahmadi is a graduate student at the University of Manitoba.