Ponente
Descripción
Ion selective electrodes are useful tools for analytical determinations of a wide variety of chemical species, since their sensitivity can be modified by using different receptors for recognition in the sensing membrane. Local characterization techniques as scanning electronic and atomic force microscopies for understanding the processes at the membrane-solution interface are particularly useful. In this work, solid-state Pb(II)-ion selective electrodes were developed, which are based on 3,3-disubstituted 1-acylthioureas as ionophores and use PVC membranes. 1-Benzoyl, 1-(2-furoyl), 3,3-diethyl and 3,3-diphenyl were the substituent groups on the thioureide core. The analytical parameters for the constructed electrodes were studied. The electrodes using 3,3-diethyl substituted thiourea derivatives as receptors showed better analytical response to Pb(II)-ions with sensitivity close to the theoretical value reported by Nernst for a divalent cation. nd an average lifetime of more than 30 days. Cu(II), Hg(II) and Ag(I) ions were interfering species during Pb(II) detection. Scanning electron microscopy and atomic force microscopy micrographs of the activated sensing membranes revealed morphological changes, which have been associated with the performance of the sensors. The studies have suggested that the presence of few large size particles or aggregates at the membrane surface is responsible for inadequate functioning of the constructed electrodes. This pattern was mainly observed for the sensing membranes based on 3,3-diphenyl groups as substituents and is related to unfavorable steric and electronic factors.
