Electrochemical determination of Pb2+ and Cd2+ with a poly(pyrrole-1-carboxylic acid) modified electrode

A pencil graphite electrode (PGE) was modified by the electropolymerization of pyrrole-1-carboxylic acid (Py-CO2) to form a sensing film of poly(pyrrole-1-carboxylic acid) (PPy-CO2) for the sensitive determination of Pb2+ and Cd2+ by differential pulse anodic stripping voltammetry (DPASV). The porous structure of the PPy-CO2 film uniformly distributes a carboxylate group throughout the coating to selectively coordinate and preconcentrate metal ions. The polymer film was characterized by cyclic voltammetry (CV), scanning electron microscopy (SEM), and energy dispersive X-ray (EDS) and Fourier transform infrared (FTIR) spectroscopy. Under the optimized conditions (analyte solution pH: 6.0, extraction time: 15 min, reduction potential: -1.1 V and reduction time: 160 s), a linear relationship between peak current and metal concentration was obtained from 0.1 to 1 nM for Pb2+ and Cd2+ with detection limits of 0.018 and 0.023 nM, respectively. Simultaneous analysis of Pb2+ and Cd2+ was performed in the presence of the possible interfering ions Cr3+, Bi3+, Cu2+, Fe2+, Zn2+ and Co2+ and in complex matrices. The performance of the PPy-CO2@PGE demonstrated excellent intra-day repeatability, long-term reproducibility over a seven-week period and was utilized for the determination of Pb2+ and Cd2+ in a variety of natural water samples with the results independently verified by inductively coupled plasma-mass spectrometry.