Amino-functionalized MCM-41 for the simultaneous electrochemical determination of trace lead and cadmium

In this work, a new strategy for the simultaneous determination of Pb2+ and Cd2+ was described based on amino-functionalized mesoporous silica (NH2-MCM-41) as sensing mediator. NH2-MCM-41 was prepared using a post-grafting process and the successful amino-functionality was confirmed by Fourier transform infrared (FTIR) and X-ray energy dispersive (EDS) spectra. It was found that both MCM-41- and NH2-MCM-41-modified glassy carbon (GC) electrode exhibit simultaneous response to Pb2+ and Cd2+. However, the NH2-MCM-41 modified electrode showed higher sensitivity than that of the MCM-41-modified one, which was attributed to the good chelating ability of amino groups to metal ions besides the high surface area and special mesoporous morphology of MCM-41. As a result, simultaneous assay of Pb2+ and Cd2+ was realized using anodic stripping voltammetric (ASV) method. Under the optimum experimental conditions, the linear response ranges for Pb2+ and Cd2+ ions are 0.5-250 μgL−1 and 50-450 μgL−1, respectively. The corresponding detection limits are 0.2 μgL−1 for Pb2+ and 1.0 μgL−1 for Cd2+, with good electrode renewability, which is defined as the complete removal of the accumulated metals from the electrode surface. In addition, the NH2-MCM-41 modified electrode was demonstrated for the successful determination of Pb2+ and Cd2+ in real samples, including tap water, lake water and tea.