Potentiometric and computer studies of yttrium-EDTMP

De Witt, G.C., May, P.M., Webb, J. and Hefter, G. (1998) Potentiometric and computer studies of yttrium-EDTMP. Inorganica Chimica Acta (275-276). pp. 39-42.

Abstract

The metal complex, Y-EDTMP (EDTMP=ethylenediaminetetra(methylenephosphonic) acid) has been evaluated as a bone therapeutic radiopharmaceutical. Its solution chemistry has been characterised in order to model its speciation in blood plasma and to compare it with that of Sm-EDTMP. The formation constants of the complexes of Y-EDTMP were measured by glass electrode potentiometry at 25°C in 0.15 M NaCl. The following values were obtained: log β11-1 ([Y(EDTMP)H-1]6-) = 3.935, log β110 ([YEDTMP]5-) = 11.106, log β111 ([Y(EDTMP)H]4-) = 17.001 and log β112 ([Y(EDTMP)H2]3-) = 22.808. Computer simulations indicate that [YEDTMP]5- and the hydroxy species [Y(EDTMP)H-1]6- are the major yttrium(III) complexes and that calcium ions are probably the major competitor for EDTMP in blood plasma.