A New Europium(III) PVC Membrane Potentiometric Sensor Based on 4-(2-Hydroxybenzylideneamino)-6-methyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one

A new europium ion-selective electrode based on 4-(2-hydroxybenzylideneamino)-6-methyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one (HMTDT) as membrane carrier was prepared. The electrode has a wide concentration range between 1.0 × 10−1 and 1.0 × 10−6 mol dm−3 with a near-Nernstian slope of 19.7 ± 0.4 mV per decade and a detection limit of 7.8 × 10−7 mol dm−3. The potentiometric response is independent of the pH of the solution in the pH range 3.5–7.8. It has a relatively fast response time and can be used for at least 2 months without any considerable divergence in potentials. The proposed sensor had very good selectivities for a wide variety of metal ions. The practical utility of the electrodes has been demonstrated by their use as indicator electrodes in the potentiometric titration of Eu3+ ions with EDTA and for the determination of Eu3+ in different solutions.