Capillary electrochromatography with 1.8-μm ODS-modified porous silica particles

The feasibility of capillary electrochromatography with 1.8-mu m ODS-modified porous Zorbax particles was studied. It appeared not possible to prepare stable frits from this material by in situ sintering; therefore, frits were made from another packing material. Addition of sodium 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 phase composition on electroosmotic mobility and plate heights was investigated. The electroosmotic mobility was almost constant in the pH range 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-porous ODS modified particles, capacity factors were 12-15-times higher, while the observed loading capacity of the particles was approximately 50-times larger. (C) 1998 Elsevier Science B.V. All rights reserved.