Copper potentiometric sensors based on copper complexes containing thiohydrazone and thiosemicarbazone ligands

Carbon paste ion-selective electrodes based on complexes of copper with the macrocyclic 3,4,10,11-tetraphenyl-1,2,5,8,9,12,13-octaaza-cyclotetra-deca- 7,14-dithizone-2,4,9,11-tetraene, L-1, and benzilbisthiosemicarbazone, L-2, were constructed for copper determination. The calibration graphs were lin ear for a wide concentration range (1x10(-5)-1x10(-2) mol l(-1)). The limit s of detection for Cu-L-1 (1:1) and (1:2) complexes were pCu=5.2 and 4.8, w hereas for Cu-L-2 (1:1) and (1:2) complexes were pCu=5.6 and 4.8, respectiv ely. Selectivity coefficients were tabulated. The response times for these electrodes were fast and stable potentials were obtained within 2-18 s for concentrations higher than 10(-4) mol l(-1). The electrodes were applied to potentiometric titrations of humic acids with copper(II) and show promise for the determination of complexation characteristic of these compounds. (C ) 1999 Elsevier Science B.V. All rights reserved.