Lipophilic Lanthanide Tris(β-diketonate) Complexes as an Ionophore for Cl- Anion-Selective Electrodes

A series of novel anion-selective electrodes were developed by incorporating lipophilic lanthanide tris(beta-diketonates) into plasticized poly(vinyl chloride) membranes. The new electrodes exhibited high selectivity toward Cl(-) anion in the concentration range of Cl(-) anion between 1.0 x 10(-5) and 1.0 x 10(-1) mol/L with near-Nernstian slopes and practically low detection limits. They offered non-Hofmeister anion selectivity, and interestingly discriminated Cl(-) anion from NO(3)(-), ClO(4)(-), and other anions. Since the employed lanthanide tris(beta-diketonates) were confirmed to form 1:1 highly coordinated complexes with Cl(-) anion, the observed high selectivity for Cl(-) anion was attributed to the characteristics of lanthanide coordination chemistry. All the prepared sensors worked well at neutral pH with quite short response time, <30 s, and could be used for longer than four months without any significant divergence in performance.