Lanthanide Recognition: an Asymetric Erbium Microsensor Based on a Hydrazone Derivative

N'-(2-hydroxy-1,2-diphenylethylidene)benzohydrazide (HDB) was found to have a very selective and sensitive behavior towards erbium(III) ions, in comparison to thirteen lanthanide ions, inner transition and representative metal ions and was hence used as a neutral ion carrier in construction of an Er(III) microelectrode. Theoretical calculations and conductance studies of HDB to erbium and some other metal ions were carried out and confirmed selectivity toward Er(III) ions. The best performance was obtained with a membrane contain 3% potassium tetrakis(p-chlorophenyl)borate (KTpClPB) as an anionic additive, 72% dibutyl phthalate (DBP) as solvent mediator, 5% HDB, and 20% poly(vinyl chloride) (PVC). The proposed Er(III) microelectrode exhibits a near Nernstian response of 17.5±0.5 mV per decade of erbium activity, and a very wide linear range 1.0×10(-3)-3.0×10(-10) M. It can work well in the pH range of 3.0-9.0. The lower detection limit (LDL) of the microelectrode was calculated to be 2.0×10(-10) M.