Use of 5,10,15,20-tetrakis(p-chlorophenyl)porphyrin as sensor material: potentiometric determination of aluminium(III) ions

In this study, 5,10,15,20-tetrakis(p-chlorophenyl)porphyrin has been synthesized and used as an ionophore for the preparation of a poly(vinyl chloride) (PVC) membrane sensor for aluminium(III) ions. The optimum composition of the best performing membrane contained ionophore, bis(2-ethylhexyl) adipate, PVC and potassium tetrakis(p-chlor- ophenyl) borate in the ratio of 4.0:63.0:32.0:1.0 (mg). The prepared PVC membrane morphology has been analysed by scanning electron microscopy. The developed aluminium(III)-selective sensor works in a wide linear concentration range of 1.0 x 10^-5 to 1.0 x 10^-1 mol l^-1 and, the detection limit of this sensor is 2.81 x 10^-6 mol l^-1. The sensor displays near-Nernstian slope of 25.0 ± 2.7 mV per decade for Al³⁺ ions. The aluminium(III)-selective sensor has a wide working pH range of 5.0–10.0. The sensor shows good reusability, long-term stability and a fast response time of less than 5 s. In addition, the sensor shows good selectivity for Al³⁺ ions over different cations. This aluminium(III)-selective sensor was successfully used as an indicator electrode in the potentiometric titration of Al³⁺ ions with EDTA. The developed sensor was successfully applied to the direct determination of Al³⁺ in different water samples. (author)