acquisition and treatment employed HP ChemStation
software (rev A.06.01). Fused silica capillaries (Polymicro
Technologies, Phoenix, AZ, USA) with dimensions
48.5-cm total length, 40-cm effective length, 75-μm i.d.,
and 375-μm o.d. were used. Samples were injected
hydrodynamically at 30 mbar for 12 s, and the detection
wavelength was set at 210 nm. The applied voltage was set
to −10 kV. On a daily basis prior to the first analysis of the
day, the capillary was conditioned by flushing with
1 mol L−1 NaOH solution for 5 min, followed by a 5-min
flush with deionized water and a 40-min flush with
electrolyte solution. The capillary was rinsed with fresh
electrolyte solution for 3 min before each run.