Azo calix[4]arene based neodymium(III)-selective PVC membrane sensor

We found that the PVC membrane, containing azo calix[4]arene is a suitable ionophore, exhibited a Nernstian response for neodymium (Nd3+) ions (with slope of 19.8 ± 0.2 mV decade−1 for the triply charged ion) over a wide linear range of 4.0 × 10−8 to 1.0 × 10−1 mol L−1 with a detection limit 1.0 × 10−8 mol L−1, a relatively fast response time, in the whole concentration range (<10 s), and a considerable life time at least for four months in the pH range of 4.0–8.0. Furthermore, the electrode revealed high selectivity with respect to all the common alkali, alkaline earth, transition and heavy metal ions, including the members of the lanthanide family other than Nd3+. Concerning its applications, it was effectively employed for the determination of neodymium ions in industrial waste water as well as in lake water.