Potentiometric determination of tanatalum with a hexafluorotantalate(V) -selective liquid membrane electrode

Brilliant Green-hexafluorotantalate(V) extract in nitrobenzene was used as electroactive material to prepare a hexafluorotantalate(V) -selective liquid membrane electrode with a PVC support. The electrode body was made from concentric polypropylene tubes which were joined by a cork. The liquid membrane electrode was connected with fluoride-selective electrode as internal reference and ground glass diaphragm (AgAgCl) electrode as external reference electrode to obtain a complete cell assembly for the potential measurements. The concentrations of sulphuric and hydrofluoric acid, for the optimum response of the electrode to hexafluorotantalate(V), were found to be 1 M each in the test solutions. The electrode was found to respond to hexafluorotantalate(V) in the concentration range of 2.0 × 10−6−1.0 × 10−2 M tantalum(V) with a slope of − 59 mV per decade and detection limit of 3.7 × 10−7 M tantalum(V) within 20–120 s. The effects of forty diverse ions on the electrode response to the hexafluorotantalate(V) have been studied and the electrode has been found to be highly selective to hexafluorotantalate(V). The newly developed liquid membrane electrode has been applied successfully to the determination of tantalum in tantalite-columbite ores by direct, sample addition, standard addition, and Granʹs plot potentiometric techniques.