Size- and charge-selective ion transfer across the zeolite-Y-modified interface between two immiscible electrolyte solutions (ZM-ITIES) is described. The zeolite-Y membrane is prepared from pressed disks by healing with tetraethyl orthosilicate (TEOS). Size- and charge-selective transfer of the tetraethylammonium cation, size-selective exclusion of tetrabutylammonium cation, and charge-selective exclusion of the tetrafluoroborate and perchlorate anions are demonstrated at the ZM-ITIES. The exclusion studies suggest that the membrane is coherent and contains a low density of pinholes, after healing with TEOS. Various factors affecting the ion transfer such as analyte concentration, supporting electrolyte concentration, and scan rate are investigated. The diffusion coefficient of tetraethylammonium ions within the zeolite-Y pores is found to be on the order of 10-8 cm2 s-1. © 2007 American Chemical Society.