A drying step in the protocol to pack capillary columns by centripetal forces for capillary electrochromatography

Capillary columns have been packed for capillary electrochromatography (CEC) using centripetal forces. The packed columns were maintained under wet conditions or they were dried with nitrogen gas prior to forming the retaining frits. Upon fabrication of the retaining frits, the dried columns were resolvated with the mobile phase. The performance of the columns was evaluated to determine the effect of the drying step during the packing procedure. The columns submitted to the drying step showed improved separation efficiencies and stronger retention characteristics than those kept under wet conditions. The drying step allows the silica-based packing material to be better accommodated inside the capillary column. Upon solvation, the packing material "swells," resulting in a greater packing density, which allows for a stronger retention and improved separation efficiencies. The drying step led to a 13% increase in retention on columns packed with isopropanol. An increase of 15-20% in theoretical plates for the most retained compounds was also observed in such columns.