A novel electrochemical sensor for simultaneous determination of cadmium and lead using graphite electrodes modified with poly(p-coumaric acid)

Abstract

In this study, we developed a new electrochemical sensor using graphite electrodes (GE) modified with poly(p-coumaric acid) (polyPCA) for simultaneous determination of Pb2+ and Cd2+ using square-wave anodic stripping voltammetry (SWASV). The GE modification was carried by electropolymerization of PCA by cyclic voltammetry. The conditions of electropolymerization as the concentration of the monomer, the number of potential cycles, scan rate, and pH electrolyte were optimized. The best responses for the detection of both metals were found using a 2.5 mM PCA solution in 0.10 M NaOH with 25 successive potential cycles at 50 mV/s in the potential range of − 0.25 to + 0.8 V. The conditions optimized for detection were deposition potential of − 1.6 V (125 s), a step of 2 mV, modulation amplitude of 80 mV, frequency of 5 Hz, and potential scan from − 0.9 to − 0.3 V. The modified electrode exhibited a linear range for simultaneous determination for Cd2+ and Pb2+ from 40 to 1000 µg/L with a limit of detection of 15.4 and 13.6 µg/L for Cd2+ and Pb2+, respectively, under optimized conditions. Furthermore, the polyPCA/GE displays satisfying selectivity (<12%) in the presence of potentially interfering other metal ions, stability for 90 days (maintaining 85% of the initial response), repeatability with a relative standard deviation (RSD) for Ipa of 1.92% for Cd2+ and 1.56% for Pb2+ (n = 10), and reproducibility of electrodes with an RSD of the 7.4% and 5.3% for Cd2+and Pb2+, respectively (n = 6). The modified electrode was applied in freshwater and water samples, including different amounts of cadmium and lead spiked into the samples. Recoveries ranging between 95 and 108% were obtained. With this approach, the electrochemical sensor proved to be a promising material for the simultaneous determination of lead and cadmium ions at the trace level.