Abstract: A new method for the detection of trace amounts of microcystins (MCs) in drinking water sources by capillary electrophoresis (CE) coupled with ultraviolet/visible light diode array detector (DAD) system was established and compared with the high performance liquid chromatography (HPLC) described in the Chinese standard method (GB/T 20466—2006). CE detection conditions were determined as follows: an uncoated fused-silica capillary tube (60 cm × 75 μm i.d.) with effective length of 44 cm as stationary phase, 12 mmol/L sodium borate solution (pH 9.0) as running buffer, separation voltage of 25 kV, sample injection under 6 895 Pa for 5 s, and detection wavelength of 238 nm. The HPLC method was performed with a C18 chromatographic column (250 mm × 4.6 mm i.d., 5 μm) using methanol: phosphate buffer solution (60:40, V/V) as mobile phase at a flow rate of 1 mL/min. The column temperature was set at 35 ℃, and the analyte was detected at 238 nm. The limits of detection (LOD) of the CE method for MC-RR, MC-LR and MC-YR were 0.16, 0.20 and 0.24 μg/mL, and those of the HPLC method were 0.020, 0.079, and 0.052 μg/mL, respectively. The sensitivity of the two methods differed by 1 order of magnitude. The recoveries of the CE and HPLC methods for three MCs were in range of 92.5%–106.0% and 99.6%–102.5%, respectively. The corresponding relative standard deviations (RSDs) of retention time and peak area were 0.53%–0.64% and 2.67%–3.29% for CE and 0.16%–0.53% and 0.80%–1.53% for HPLC, respectively. For the same water sample, the MCs content determined by CE was not significantly different from that determined by HPLC (P > 0.05).

Key words: capillary electrophoresis (CE), high performance liquid chromatography (HPLC), microcystins (MCs), detection