Lanthanum-selective membrane electrode based on 2,2′-dithiodipyridine

In this study, a new poly(vinyl chloride) (PVC) membrane sensor for La3+ ion based on 2,2′-dithiodipyridine as an ion carrier was prepared. This electrode revealed good selectivity for La3+ over a wide variety of other metal ions. Effects of experimental parameters such as membrane composition, nature and amount of plasticizer, the amount of additive and concentration of internal solution on the potential response of La3+ sensor were investigated. The electrode exhibited a Nernstian slope of 20.0 ± 1.0 mV per decade of La3+ over a concentration range of 7.1 × 10−6 to 2.2 × 10−2 M of La3+ in the pH range 3.3-8.0. The response time was about 7 s and the detection limit was 3.1 × 10−6 M. The electrode can be used for at least 2 months without a considerable divergence in potential. The proposed electrode was used as an indicator electrode in potentiometric titration of oxalate and fluoride ions and was applied for determination of F− ion in mouthwash solution.