Determination of Cr3+ ions in biological and environmental samples by a chromium(III) membrane sensor based on 5-amino-1-phenyl-1H-pyrazole-4-carboxamide Original Research Article

A highly Cr3+-selective ionophore, based on 5-amino-1-phenyl-1H-pyrazole-4-carboxamide (APC) as a carrier, was synthesized in order to obtain a Cr3+ ion-selective electrode. The demonstrated characteristics of the sensor included a linear dynamic range between 1.0 × 10− 6 and 1.0 × 10− 1 M with a near Nernstian slope of 19.6 ± 0.4 mV per decade, a detection limit of 5.3 × 10− 7 M, a very good selectivity for Cr3+ over other cations in a wide pH range (3.2–6.3). Furthermore, the newly-designed electrode presented a fast response time of 10 s with a lifetime of at least 2 months indicating no considerable potential divergence. The sensor accuracy was investigated by the potentiometric titration of a Cr(III) solution with EDTA as well as the monitoring of Cr(III) in mixtures of three and five different ions. As a result, the developed sensor provided satisfactory results after its application in the Cr3+ determination in biological samples (urine and synthetic plasma) and also in wastewater of chromium electroplating industries.