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

Abstract 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, L1, and benzilbisthiosemicarbazone, L2, were constructed for copper determination. The calibration graphs were linear for a wide concentration range (1×10−5–1×10−2 mol l−1). The limits of detection for Cu–L1 (1:1) and (1:2) complexes were pCu=5.2 and 4.8, whereas for Cu–L2 (1:1) and (1:2) complexes were pCu=5.6 and 4.8, respectively. 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.