Zinc(II) modified carbon paste electrodes based on self-assembled mercapto compounds-gold-nanoparticles for its determination in water samples

In the present study newly developed potentiometric sensors for determination of zinc(II) are presented. The proposed potentiometric method was based on the fabrication of modified carbon paste (MCPE; electrode X) and modified gold nanoparticles-carbon paste (GNPs-CPE; electrode IX) sensors. A mercapto compound of 1,4-bis(5-mercaptopentyloxy)-benzene (BMPB) alone or self-assembled on gold nanoparticles was used as modifier to construct electrode (X) and electrode (IX) sensors, respectively. The prepared electrodes exhibit Nernstian slope of 29.93 ± 0.4 and 26.0 ± 1.02 mV decade−1 towards Zn(II) ion over a wide concentration range of 6.8 × 10−10 to 2.9 × 10−2 and 1.0 × 10−7 to 1.0 × 10−2 mol L−1 for electrode (IX) and electrode (X) sensors, respectively. The limit of detection of the electrode (IX) and electrode (X) sensors was found to be 6.8 × 10−10 and 1.0 × 10−7 mol L−1, respectively. The potentiometric response of the electrode (IX) and electrode (X) based on GNPs-BMPB and BMPB are independent of pH of test solution in the pH range of 2.5–8.1 and 3–7 with a response time of 6 and 8 s for electrode (IX) and electrode (X) sensors, respectively. The proposed sensors showed fairly good discriminating ability towards Zn(II) ion in comparison with many hard and soft metal ions. Finally, the proposed electrodes were successfully used as indicator electrodes in potentiometric titration of zinc ion with sodium tetraphenylborate (NaTPB) and in direct determination of Zn(II) ion in some water samples. The results obtained compared well with those obtained using atomic absorption spectrometry.