Selectivity of potentiometric sensors integrated with paper-based solution sampling for determination of heavy metals in environmental samples containing high solid to liquid ratios

• Main Author: Yip, Jane Si Qi
• Other Authors: Grzegorz Lisak
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Environmental engineering
• Online Access: https://hdl.handle.net/10356/163714
• Institution: Nanyang Technological University

Paper-based potentiometry is a promising technique for determination of heavy metal in samples containing high solid to liquid ratios. There have been various parameters used to determine the performance of Pb2+-ISEs coupled with paper-based potentiometry, such as potentiometric working range and slope. As selectivity is an important parameter characterizing ISEs that presents the ability of the electrode to detect the target primary ion in the presence of other interfering ions. Pb2+-ISEs were used to investigate the different responses of metal ion sample solutions on paper-based sampling. However, there are some challenges in the determination of heavy metals in samples which are connected to the inherent interactions between paper substates and the analyte causing a super-Nernstian response of the heavy metal sensitive ISEs. In this work, several paper substrate modifications were selected for this study, namely metal sputtering, acidified, ion-selective membrane and inorganic salt paper substrates. It was determined that the various paper modification showed similar results in terms of Cd2+ as the most interfering metal ion and Mg2+ as least interfering metal ion. The results from these modifications also had similar ion sequence with only a few slight shifts in positions but it was insignificant. The selectivity coefficient values were also consistent throughout the different trials except for the inorganic salt (Pb2+) paper-based modification which had the most unstable and inconsistent values. This could be due to the presence of Pb2+ ion in the paper substrates causing an interaction with other metal ions from the sample solution during the experiment. Furthermore, trials were carried out with electrodes containing only PEDOT(PSS) layer to further investigate the interaction of Pb2+ ion from the paper substrate with the metal ions from the sample solution.