Holmium(III)-selective fluorimetric optode based on N,N-bis(salicylidene)-naphthylene-1,8-diamine as a neutral...

For the first time a highly sensitive and selective fluorimetric optode for determination of trace amounts of Ho(3+) ions was prepared. The sensing system was prepared by incorporating of N,N-bis(salicylidene)-naphthylene-1,8-diamine (L) as a neutral Ho(3+)-selective fluoroionophore, in a plasticized PVC membrane containing sodium tetraphenyl borate as a lipophilic anionic additive. The response of the sensor is based on the strong fluorescence quenching of L by Ho(3+) ions. At pH 5.4, the proposed sensor displays a calibration curve over a wide concentration range of 1.0×10(-10)-1.0×10(-3)M, with a relatively fast response time of less than 1 min. In addition to high stability, high reproducibility and a relatively long working lifetime, the sensor shows a good selectivity towards Ho(3+) ion with respect to common coexisting cations. The fluorescence optode was applied to determination of holmium ion contents of water samples.