Abstract: The quaternary phosphonium compounds are promising site materials for the preparation of anion-sensitive electrodes. Many phosphonium counter-parts of quaternary ammonium salts are difficult to be synthesized and the simplified methods searching for synthesis of useful quaternary phosphonium site materials are of considerable interest. Several such phosphonium compounds have been synthesized and compared as site materials for anion-sensitive membranes. Hexadecyltriphenylphosphonium iodide (HTPP) was recommended as especially suitable substance for this purpose. Asimple method for synthesis of HTPPfrom triphenylphosphine and hexadecyl iodide was worked out. The electrodes prepared from HTPP are equal or superior in sensitivity to the early quaternary ammonium site versions. The membrane composition for various anions was optimized. The potentiometric selectivity coefficients of the prepared electrodes and their correlation with various ionic parameters have also been investigated.