Fabrication of new carbon paste electrodes based on gold nano-particles self-assembled to mercapto compounds as suitable ionophores for potentiometric determination of Copper ions

In the present study, we investigate the potentiometric behavior of Cu2+ carbon paste electrodes based on two mercapto compounds 2-Ethylmino-5-Mercapto-1,3,4-Thiadiazole (EAMT) and 2-Acetylamino-5-mercapto-1,3,4-thiadiazole (AAMT) self-assembled on gold nano-paricle (GNP) as ionophore. Then, the results obtained from the modified electrodes are compared. The self-assembled ionophores exhibit a high selectivity for Copper ion (Cu2+), in which the sulfur and nitrogen atoms in their structure play a role as the effective coordination donor site for the Copper ion. Among these electrodes, the best performance was obtained with the sensor with a EAMT/graphite powder/paraffin oil weight ratio of 4.0/68/28 with 200 µL of GNP exhibits the working concentration range of 1.6×10−9 to 6.3×10−2 M and a Nernstian slope of 28.9±0.4 mVdecade−1 of copper (II) activity. The detection limit of electrode was 8.9(±0.2)×10−10 M and potential response was pH independent across the range of 2.8–6.3. The proposed electrode presented very good selectivity and sensitivity towards the Cu2+ ions over a wide variety of cations including alkali, alkaline earth, transition and heavy metal ions. Also the proposed electrode was successfully applied as an indicator electrode in the potentiometric titration of Cu (II) ions with EDTA and the potentiometric determination of copper ions in spiked water samples.