AbstractUnder the influence of an electric field, trialkyltin compounds of the type R3SnX behave as electrically neutral carriers for anions in poly(vinyl chloride) liquid membranes. The interaction of tinorganic compounds with oxoanions was studied in organic phase by means of119Sn‐NMR‐monitored titrations. In the case of tributyltin chloride, no appreciable amount of complex was formed with hydrogensulfate, whereas dihydrogenphosphate gave rise to a new species. Dioctyltin dichloride and dioctyltin dioctyltin diacetate formed a 1:2 (salt/ligand) complex with hydrogenphosphate.