CE analysis
CE was performed on an Hp3DCE instrument (Agilent Technologies, Waldbronn,Germany) with a built-in diode array detector, Separation and analysis were carried out on an uncoated fused silica capillary tube (50 m i.d.,64.5 cm total length, and 56 cm effective length) at 25 C. Before its first use,the fused silica capliiary was washed with 1.0 M NaOH for 5 min,with H2O for 5 min, and with the operating buffer for 10 min. Before each run, the capillary tube wass washed with 00.1 M NaOH for 1 min. After each analysis, the capillary was postconditioned with H2O for 2 min. Before use, the operating buffer was filtered through a 0.2-m membrane filter and degassed with agitation in an ultrasonic bath.