Abstract: Remarkable progress has been achieved in the development of electrodes sensing various anions since the introduction of quaternary ammonium salts as carriers.Question remains,however,as to the preparation of electrodes sensing the phosphate ion.In this report,bis(tribenzyltin) oxide is tested as a carrier for phosphate ions.Liquid membrane containing this carrier,o-nitrophenyl octyl ether as plasticizer,and poly(vinyl chloride)(PVC) as membrane matrix showed Nernstian response for hydrogen phosphate in the 5×10^-6 mol/Lto 10^-1 mol/Lactivity range with a slope of-30.1 mV/dec.in pH=7.2±0.02 solutions.The electrode displayed selectivity patterns sequence:HPO₄^2-～I^->Br^->NO₃^->Cl^->Ac^->SO₄^2-,which is not in accordance with the selectivity sequence pattern obtained from classical anion exchangers.Also included here is the comparison of potentiometric response characteristics between the binuclear and mononuclear organotin compounds,An enhanced response towards from binuclear compound based electrode was observed,showing that binuclear organometallic compounds may become a new promising class of carrier for anions.

Key words: Binuclear organotin compound, Hydrogen phosphate, Ion sensitive electrode