Abstract:

A sensitive and simple method based on capillary electrophoresis (CE) with electrochemiluminescence (ECL)
detection has been developed for the separation and determination of rhodamine B in chili power. The effects of detection
potential, the concentration of Ru(bpy)3
2+, the acidity and concentration of the running buffer, separation voltage and
injection time were investigated to acquire the optimum conditions. The detection electrode was a 300 μm diameter platinum
microelectrode at a detection potential of 1.14 V (versus Ag/AgCl). Rhodamine B could be well separated within 6 min in a
50 cm length fused-silica capillary at a separation voltage of 15 kV in a 20 mmol/L PBS buffer (pH 8.0). The response range
of rhodamine B was from 5 × 10-7 to 5 × 10-5 mol/L with a detection limit of 1 × 10-7 mol/L (RSN = 3). The proposed method
demonstrated long-term stability and reproducibility with relative standard deviations (RSD) of less than 3.5% for both
migration time and electrophoretic peak area (n = 5). This method can be successfully applied to the analysis of rhodamine B
in chili power with satisfactory assay results.

Key words: capillary electrophoresis, electrochemiluminescence, chili power, rhodamine B