The separation was proceeded in a 75 cm length of 25-mm i.d. and 360-mm o.d. fused
silica capillary (Polymicro Technologies, Phonix, AZ,USA). In order to protect the operator from the high voltage and assure the safety of the CE-ED system, the
entire capillary, the buer reservoir for CE, and all electrodes were enclosed in a Plexiglas box with a safety switch wired to turn o the power supply whenever the
box was opened (Ye & Richard, 1993, Ye & Richard,1994).