A set of seven homemade octadecyl silica-based bonded phases was investigated. Their zeta potential data in methanol and ACN as well as in methanol-water and ACN-water solution were obtained using Zetasizer. The influence of both the coverage density of bonded ligands and the end-capping of the modified surface on these data was investigated. Presented results may give useful information about the accessibility of the residual silanols in different mobile phases during the chromatographic analysis. Those measurements may be useful to choose chemically bonded stationary phases for CEC. The results also confirm the phenomena of anion exclusion from the pores of stationary-bonded phase.