In recent years the complexation of many transition and heavy metal ions with several proton transfer systems including pyridine-2,6- diamine, melamine, creatinine, 2-aminopyrimidine / dipicolonic acid(pydc)[1-4]were studied in solid state and solution, but the interaction of this proton transfer system with alkaline earth wasn't attended. In this work the complexation constants and stoichiometry of piperazine-dipicolonic acid system with Sr2+ ion in aqueous solution at 25.0 ± 0.1°C and ionic strength of 0.1M supported by NaNO3 were investigated by potentiometric pH titrations. The overall stability constant, logarithm of -values, of all species present were evaluated by computer refinement of pH-volume data using the BEST computer program[5].Distribution diagrams depicted using Hyss2009 program[6]. The observed species of pydc(L)-Sr and piperazine(Q)-Sr, binary species are: SrL, SrL2, SrLH, SrQ2 and SrQH. It was seen for the pydc-piperazin-Sr, ternary species are: SrLQH2, SrLQH3 and SrLQ2H. The stoichiometry of one of the most abundant complexes species in solution was found to be similar to the crystalline strontium complex..
