Evidence of Eu(III) Dual Binding in a PVC-Based Electrochemical Sensor with N,N,N',N'-Tetrapentyl Diglycolamide (TPDGA) as the Ionophore: Potentiometric and Luminescence studies

The present investigation deals with the development of a polyvinyl chloride (PVC) based potentiometric sensor for Eu(III) containing N,N,N',N'-tetrapentyl diglycolamide (TPDGA) as ionophore, 2-nitrophenyl octylether (NPOE) as plasticizer and sodium tetraphenylborate (NaTPB) as ionic additive. The membrane with 8.7 % TPDGA, 29.7 % PVC, 59.0 % NPOE, 2.5 % NaTPB exhibited a linear response behaviour from 1.5x10(-6) m to 1.1x10(-2) m Eu(III) with a slope of 23.4 +/- 0.3 mV/decade and a limit of detection (LOD) of 1.2x10(-6) m. The sensor showed fast response times (<5 s) and a lifetime of two months. It showed good tolerance for monovalent/divalent interfering ions and moderate/poor tolerance for trivalent ions. The membrane was characterized using photoluminesce (PL) spectroscopy which suggested NPOE can alter the nature of species in the membrane and evidence the presence of two species. The membrane can be used as an indicator electrode for the potentiometric titration of Eu(III) and in the estimation of europium in the synthetic and laboratory bearing waste which compared well with the x-ray fluorescene (XRF) results.