A highly efficient sensor for europium(III) estimation using a poly(propylene imine) diaminobutane diglycolamide dendrimer as the ionophore: Potentiometric and photoluminescence studies

Multiple-diglycolamide (DGA) based ligands are known as highly promising extractants for the selective and efficient extraction of trivalent lanthanides/actinides from acidic feed solutions and therefore they have a great potential for the low level detection of these metal ions when used as ionophores in a potentiometric sensor. However, their use as ionophores in a potentiometric sensor is not much explored. Here in, we report the potentiometric sensing of Eu(III) ion in acidic medium using three novel multiple DGA-functionalized dendrimers: viz., generation zero (G₀), one (G₁) and two (G₂) poly(propylene imine) diaminobutane dendrimers as ionophores doped in a polyvinyl chloride (PVC) matrix containing 2-nitrophenyl octyl ether (NPOE) as the plasticizer and sodium tetraphenylborate (NaTPB) as the ionic additive. Out of these three dendrimers, the G₁ membrane gave very encouraging results and the G₂ membrane did not work properly. On the other hand, the G₀ membrane showed a narrower linear dynamic range (LDR), and a higher limit of detection (LOD) than the G₁ membrane. The membrane with 4.1 % G₁, 31.1 % PVC, 62.2 % NPOE, 2.6 % NaTPB exhibited a linear response behaviour from 6.6 × 10^-7 M to 1.5 × 10^-2 M Eu(III) with a slope of 15.6 ± 0.2 mV/decade and a LOD of 5.0 × 10^-7 M. The response time and lifetime of this sensor were found to be < 10 s and more than three months, respectively, and showed reasonably high selectivity with respect to mono- and divalent cations as well as the uranyl ion. All the sensor membranes contained two types of Eu(III) species as seen by luminescence spectroscopy. The sensor efficiency was checked by the ‘spike recovery method’. The G₁ membrane sensor was also employed for the potentiometric titration of Eu(III) as an indicator electrode. Both methods showed more than 95 % recovery with excellent matching with the X-ray fluorescence (XRF) results. The sensor can also be used in the estimation of europium ion in a laboratory bearing waste and in a lamp phosphor waste leached which compared well with XRF and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) results, respectively.