On-Line Electrokinetic Supercharging and Sweeping for the Preconcentration and Determination of Nucleosides and Related Compounds by Capillary Electrophoresis

Abstract

Nucleosides and related compounds have vital physiological and pharmacological activities. In this study, on-line preconcentration using electrokinetic supercharging (EKS)-sweeping method was proposed to enhance the efficiency of the capillary electrophoresis separation of the nucleosides and related compounds. The separation conditions, including the pH of the borate buffer (terminating electrolyte), the concentration and pH of the phosphate buffer (leading electrolyte), the concentration of sodium dodecyl sulfate (SDS) and the electrokinetic injection (EKI) time, were investigated in detail. The optimum EKS-sweeping conditions were as follows: 40 mM sodium phosphate buffer at pH 2.0 containing 50 mM SDS as the BGE, 120 mM sodium phosphate buffer at pH 2.0 as the leading electrolyte, 30 mM borate buffer at pH 12.0 as the terminating electrolyte, and EKI of the sample at −10 kV for 30 s. The separation was performed by micellar electrokinetic chromatography at −5 kV. Under these conditions, the sensitivity values of five analytes were enhanced from 26 to 109-fold compared to a standard capillary zone electrophoresis (CZE) procedure. The intra- and inter-day repeatability values (as the relative standard deviation) were less than 1.1% and 5.2% for the migration time and lower than 4.4% and 4.8% for the peak areas. Finally, the developed method was successfully applied for the determination of nucleosides and related compounds in Chinese cordyceps samples.