Simultaneous determination of phenylurea herbicides in yam by capillary electrophoresis with electrochemiluminescence detection

A method of capillary electrophoresis (CE) coupled with electrochemiluminescence (ECL) detection has been applied to detect three major phenylurea herbicides (monuron, monolinuron and diuron) simultaneously. The effects of yam sample preparation, injection voltage and time, detection potential, detection buffer concentration and pH, Ru(bpy)32+ concentration, separation buffer type, separation buffer pH and concentration, separation voltage were investigated in detail. Under optimum conditions, a good baseline separation and highly sensitive detection for monuron, monolinuron and diuron were achieved. The ECL intensity (I) was in proportion to three analytes concentration (ρ) in the range of 0.1-10,000 μg/L for monuron (r ≥ 0.9993), 0.1-18,000 μg/L for monolinuron (r ≥ 0.9995) and 0.1-20,000 μg/L for diuron (r ≥ 0.9997). The detection limits for monuron, monolinuron and diuron were 0.05, 0.04 and 0.01 μg/L (S/N = 3), respectively. The developed method was successfully applied for the analysis of monuron, monolinuron and diuron residues in yam simultaneously. The average recoveries are in the ranges of 90.0-99.2% with relative standard deviations less than 3.2%. The limits of detection of the proposed method were 0.010 μg/kg for monuron, 0.008 μg/kg for monolinuron and diuron in yam.