Sol-gel monolithic columns with reversed electroosmotic flow for capillaryelectrochromatography

Sol-gel chemistry was used to prepare porous monolithic columns for capilla ry electrochromatography. The developed sol-gel approach proved invaluable and generates monolithic columns in a simple and rapid manner. Practically any desired column length ranging from a feu tens of centimeters to a few m eters may be readily obtained. The incorporation of the sol-gel precursor, N-octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride, into the s ol solution proved to be critical as this reagent possesses an octadecyl mo iety that allows for chromatographic interactions of analytes with the mono lithic stationary phase. Additionally, this reagent served to yield a posit ively charged surface, thereby providing the relatively strong reversed ele ctroosmotic flow (EOF) in capillary electrochromatography. The enhanced per meability of the monolithic capillaries allowed for the use of such columns without the need for modifications to the commercial CE instrument. There was no need to pressurize both capillary ends during operation or to use hi gh pressures for column rinsing. With the developed procedure, no bubble fo rmation was detected during analysis with the monolithic capillaries when u sing electric held strengths of up to 300 V cm(-1). The EOF in the monolith columns was found to be dependent on the percentage of organic modifier pr esent in the mobile phase, Separation efficiencies of up to 1.75 x 10(5) pl ates/m (87 300 plates/column) were achieved on a 50 cm x 50 mu m i.d. colum n using polycyclic aromatic hydrocarbons and aromatic aldehydes and ketones as test solutes.