Highly selective and sensitive chromium(III) membrane sensors based on a new tridentate Schiff's base

In order to get a view about the tendency of N-(1-thien-2-ylethylidene)benzene-1,2-diamine (SNS), towards chromium and some other metal ions, theoretical calculations and conductance studies were carried out. Then, a highly selective and sensitive plasticized membrane sensor for chromium(III) ions, based on SNS as membrane carrier, was prepared. The sensor shows a linear dynamic range of 1.0 × 10−6 to 1.0 × 10−1 M with a Nernstian slope of 19.9 ± 0.3 mV decade−1 and a detection limit of 7.0 × 10−7 M (∼40 ppb). It has a fast response time of <12 s and can be used for at least eight weeks without any considerable divergences in its potentials. The proposed sensor revealed very good selectivities with respect to most of the common metal ions including Li, Na, K, Rb, Cs, Be, Mg, Ca, Cu, Co, Ni, Zn, Pb, Hg, Fe, La, Ce and Eu ions. The proposed sensor could be used in a pH range of 3.0–6.6. It was also used in the determination of Cr(III) in wastewater of chromium electroplating and leather industries, showing satisfactory results. The sensor was also applied for monitoring the chromium ion level in wastewater of chromate industries.