An efficient and selective flourescent optode membrane based on 7-[(5-chloro-8-hydroxy-7-quinolinyl)methyl]-5,6,7,8,9,10-hexahydro-2H-1,13,4,7,10-benzodioxatriazacyclopentadecine-3,11(4H,12H)-dione as a novel fluoroionophore for determination of cobalt(II) ions.

A novel fluorescence chemical sensor for the highly sensitive and selective determination of Co(2+) ions in aqueous solutions is prepared. The cobalt sensing system was prepared by incorporating 7-[(5-chloro-8-hydroxy-7-quinolinyl)methyl]-5,6,7,8,9,10-hexahydro-2H-1,13,4,7,10-benzodioxatriazacyclopentadecine-3,11(4H,12H)-dione (L) as a neutral cobalt-selective fluoroionophore in the plasticized PVC membrane containing sodium tetraphenylborate as a liphophilic anionic additive. The response of the sensor is based on the strong selective fluorescence quenching of L by Co(2+) ions. At a pH 5.0, the proposed sensor displays a calibration curve over a wide concentration range of 5.0 x 10(-7) to 2.0 x 10(-2)M with a relatively fast response time of less than 5 min. In addition to high stability and reproducibility, the sensor shows a unique selectivity towards Co(2+) ion with respect to common coexisting cations. The proposed fluorescence optode was successfully applied to the determination of cobalt content of vitamin B12 ampoule, cobalt cake, cobalt alloy and tap water samples.