Lead (II) selective polymeric membrane sensors based on p-Isopropylcalix[6]arene as chelating ionophore

Abstract: Lead can accumulate in soils, especially those with a high organic content, where it remains for hundreds to thousands of years. It can take the place of other metals in plants and can accumulate on their surfaces, thereby retarding photosynthesis, and preventing their growth or killing them [1]. Contamination of soils and plants then affects microorganisms and animals. Affected animals have a reduced ability to synthesize red blood cells, which causes anemia [2]. The current work deals with fabrication of Pb (II) selective electrode for quantitative determination of lead in environmental solutions. p-Isopropylcalix[6]arene has been used as an ionophore and 2-nitrophenyl octyl ether (o-NPOE) as a plasticizer in order to develop a ployemeric membrane electrode for lead (II) ion detection. The developed sensor exhibit significantly enhanced response towards lead (II) ions over the concentration range 1.0×10−6 – 1.0×10−1 M at pH 3.5-7 with a lower detection limit of 7.0×10−7 M. The sensors display Nernstian slope of 28.95 ± 0.23 mV per decade for Pb (II) ions. Effects of plasticizers, lipophilic salts and various common interfering ions are tested. It has a fast response time within 20 s over the entire concentration range and can be used for at least 3 months without any divergence in potentials. The selectivity of the sensor is comparable with those reported for other such electrodes. The proposed sensor was successfully applied as an indicator electrode for the potentiometric titration of a Pb (II) solution with EDTA.