Ion association between inorganic anions and symmetrical tetraalkylammonium ions, R 4 N + (R = Me, Et, Pr, n-Bu, n-Am, and 2-methyl butyl {isoamyl=iAm}) was investigated using ordinary silica capillary by capillary zone electrophoresis. An improved version of the Williams-Vigh method was used for the first time to measure the mobilities of the inorganic anions. Plots of log K ass against log dielectric constant in various media, revealed a smaller change in K ass compared to dielectric constant. These plots suggest that the Bjerrum's equation is inadequate in accounting for the associations of ions in a CZE setup.