Development of perchlorate-selective composite potentiometric sensor

This thesis focuses on the development of a novel all-solid-state composite ion-selective electrode (ISE) for the potentiometric determination of perchlorate ions. Methyltrioctylammonium chloride (MTOACl) salt was employed as the active component (ionophore) of the sensing electrode layer. To determine the optimal formulation of the ion-selective composite layer, composite ISEs with varying mass ratios of graphite, poly(vinyl chloride) (PVC), multi-walled carbon nanotubes (MWCNTs), plasticizer, and ionic additive were fabricated, and their potentiometric performance parameters were thoroughly investigated. The results revealed that the composite prepared using 5 mg of MTOACl, 20 mg of PVC, 40 mg of 2-nitrophenyloctyl ether (o-NPOE), and 60 mg of graphite exhibited the most superior potentiometric characteristics. The composite electrode prepared with this optimal composition demonstrated a linear response within the perchlorate concentration range of 5,0×10⁻6 to 1,0×10-1 M, a Nernstian slope of -51,5 mV/decade, a limit of detection of 2,0×10-6 M, a pH operating range of 3,5-9,0, and a response time of approximately 10 seconds. The developed electrode exhibited highly reproducible, stable, and selective potentiometric responses towards perchlorate ions. The analytical merit of the electrode was successfully demonstrated through the direct calibration method for the determination of perchlorate ion content in spiked tap water samples