A novel Holmium(III) membrane sensor based on N-(1-thien-2-ylmethylene)-1,3-benzothiazol-2-amine

A novel plasticized membrane sensor for Ho(III) ions based on N-(1-thien-2-ylmethylene)-1,3-benzothiazol-2-amine (TBA) as a neutral carrier was prepared. The best performance was obtained with a membrane composition of 31% PVC, 61% benzyle acetate, 2% sodium tetra phenyl borate and 6% carrier. The electrode exhibits a Nernstian response for Ho(III) ions over a particular concentration range (1.0x10(-5) -1.0x10(-2) M) with a slope of 19.7 +/- 0.2 mV decade(-1) . The limit of the detection is 7.0x10(-6) M. The sensor has a response time of <15 s and a useful working pH range of 4.0 - 9.5. The proposed sensor discriminates relatively well towards Ho(III) ions with regard to common alkali, alkaline earth, and specially lanthanide ions. It was successfully applied as an indicator electrode in a potentiometric titration of Ho( III) ions with EDTA. It was also applied in determination of fluoride ions in a mouth wash preparation. The proposed sensor was applied for the determination of Ho( III) ion concentration in binary mixtures.