CAPILLARY ELECTROCHROMATOGRAPHY WITH 1.8-MU-M ODS-MODIFIED POROUS SILICA PARTICLES

The feasibility of capillary electrochromatography with 1.8-mu m ODS-m odified porous Zorbax particles was studied. It appeared not possible to prepare stable frits from this material by in situ sintering; there fore, frits were made from another packing material. Addition of sodiu m dodecyl sulfate to the mobile phase was not necessary for operation of the columns without bubble formation. The columns could be operated with field strengths up to 125 kV m(-1). The effect of the mobile pha se composition on electroosmotic mobility and plate heights was invest igated. The electroosmotic mobility was almost constant in the pH rang e from 6 to 9, but declined steeply to half the value in the pH range 3-5. The ionic strength of the mobile phase had only a small effect on the plate heights and electroosmotic flow. Efficiencies up to 310 000 plates m(-1 )(h=1.7) were obtained with 80% (v/v) acetonitrile in the mobile phase. Compared to previous experiments with 1.5-mu m non-poro us ODS modified particles, capacity factors were 12-15-times higher, w hile the observed loading capacity of the particles was approximately 50-times larger. (C) 1998 Elsevier Science B.V. All rights reserved.