Preparation of a solid-state ion-selective electrode based on polypyrrole conducting polymer for magnesium ion

In this study, a potentiometric sensor based on a pencil graphite electrode (PGE) coated with polypyrrole doped with Titan yellow dye (PPy/TY) was prepared for potentiometric determination of magnesium ion in aqueous solutions. The structural characteristics of magnesium sensor electrode (PGE/PPy/TYMg) were studied using scanning electron microscopy and Fourier transform infrared along with energy-dispersive spectroscopy. Under the optimal conditions, the electrode reveals a good Nernstian behavior with slope of 28.27 ± 0.40 mV per decade over the concentration range of 1.0 × 10^?5–5.0 × 10^?2 M and a detection limit of 6.28 × 10^?6 M. The potentiometric response of fabricated electrode toward magnesium ion was found to be independent of the pH of the test solution in the pH range of 4.5–8.0. The electrode showed fast response time (<10 s) and good shelf lifetime (>2 months). The prepared magnesium sensor electrode can also be used as an indicator electrode in potentiometric titration of Mg²⁺ with EDTA with distinguished end point. The electrode revealed good selectivity with respect to many cations including alkali, alkaline earth, transition and heavy metal ions. The introduced magnesium electrode was used for measurement of Mg²⁺ ion in real samples without any serious interferences from other ions.