A poly (vinyl chloride)-based membrane of 2,9-dihydroxy-1,10-diphenoxy-4,7-dithiadecane (C20H26O4S2) as a neutral carrier was prepared and investigated as an Y3+-selective electrode. Effects of various plasticizers and anion excluders were studied in detail and improved performance was observed. The best performance was obtained for the membrane sensor having a composition of L: PVC: NPOE: PA in the ratio of 2:30:62:6 (mg). The performance of the membrane was found to be the following: A Nernstian slope of 20.0 ± 0.2 mV per decade across a broad range (1.0 × 10−9 to 1.0 × 10−1 mol dm–3); a detection limit of 2.14 × 10–10 mol dm–3 between the pH = 4.5 and 9.0; additionally, the response time was about 15 s; good Y3+ selectivity over a wide variety of other metal ions. The membrane sensor was applied as an indicator electrode in potentiometric titration of fluoride ion and also used for determination of F− ion in tap water and toothpaste samples

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