Macrocyclic ligands complexes used in the pX. Buffer solutions preparationI. Pb2+ complexes with [18]-crown-6 and dicyclohexyl [18]-crown-6

The stability-constants of Pb2+ complex with macrocyclic ethers: [18]-crown -6 and DCH-[18]-crown-6 were determined. These complexes are going to Se us ed for the preparation of the tampon-Pb2+ etalon solutions. The stability-c onstants of the studied complexes were determined by potentiometric methods and the values 1g beta 1 = 4.04+/-0.03 for the Pb2+-[18]-crown-6 complex a nd also 4.82 +/- 0,02 for Pb2+ -DCH[18]-crown-6 complex were obtained at mu = 0.03 and 25 degrees C +/- 0.1. Several characteristics of these complexes such as: formation of one single complex 1: 1(metal:ligand ratio); the neutral character of both ligands wh ich eliminates their participation to the proton transfer reactions and so eliminates the pH influence: knowing by the present study's results, the ex act values of the stability constants beta(1) in ionic strength and constan t temperature conditions: are putting the two studied complexes at the elab oration base of the Pb2+ etalon-tampon. solutions:necessary for optimizatio n of Pb2+ selective electrodes calibration in direct potentionmetric me;mea surements.