Voltammetric Detection of Lead(II) Using Amide-Cyclam-Functionalized Silica-Modified Carbon Paste Electrodes

2-(4,8,11-Triscarbamoylmethyl-1,4,8,,11-tetraazacyclotetradec-1-yl)acetamide (TETAM) derivatives bearing 1, 2, or 4 silylated arms have been synthesized and grafted to the surface of silica gel and ordered mesoporous silica samples. The resulting organic-inorganic hybrids have been incorporated into carbon paste electrodes and applied to the preconcentration electroanalysis of Pb(II). The attractive recognition properties of these cyclam derivatives functionalized with amide pendent groups toward Pb(l I) species and the highly porous structure of the adsorbents can be exploited for the selective and sensitive detection of the target analyte. Various parameters affecting the preconcentration and detection steps have been discussed with respect to the composition and pH of both accumulation and detection media, the nature of the adsorbent (number of silylated groups linking the macrocycle to silica, texture of materials), the accumulation time, and the presence of interfering cations. Under optimal conditions and for 2 min accumulation at open-circuit, the voltammetric response increased linearly with the Pb(II) concentration in a range extending from 2 x 10(-7) to 10(-5) M, while a longer accumulation time of 15 min afforded a linear calibration curve between 10(-8) and 10(-7) M with a detection limit of 2.7 x 10(-9) M which is well below the European regulatory limit of lead in consumption water.