A model of non‐nernstian response in the determination of aluminum ions by indirect potentiometry

Abstract

Flow analysis data of the response of an aluminum wire electrode to fluoride into which A13+ is added is modeled assuming a logarithmic response of the electrode to F-and reaction of F-with aluminum ions to give a series ofcomplexes [A1F,](3-9)f when q = 1,2,3,4,5,6. The solutions were maintained at pH 5.0 with acetic acid/acetate buffer. Other species modeled were the hydroxo complexes of aluminum [Al,(OH),]'3"-"'+ when m = I, n = 1,2,3,4; m = 2, n = 2; m = 3, n = 4; m = 13, n = 32, and the acetate complex [A12(0H),OAc]'+. Protonation of F-to H F and HFF was also considered. Three coefficients were required to fit the data, a constant and slope of the response of the electrode to free fluoride and a dispersion factor in the flow analysis. Published stability constants were used and no account was taken of ionic strength. The model may be used to predict optimum analysis conditions given an approximate aluminum concentration.

Flow injection potentiometric determination of Fe(III) using a fluoride-selective electrode as detector

“…Since the FISE was developed (1966), the formation constants of many metal fluoro complexes in aqueous solution have been determined. However, there are very few reports in which the FIA determination of metal ions, or their influence on the response characteristics of the fluoride ion-selective electrode, based on metal fluoride complex formation are discussed [4][5][6][7].Suitability of the FISE for monitoring a reasonably fast reaction of the formation of FeF 2+ in acidic solution has been previously established [8]. Oehme and Dolezalova [9] reported the possibility of direct potentiometric determination of Fe 3+ based on iron-fluoride complex formation but no detailed information was given.…”

“…Since the FISE was developed (1966), the formation constants of many metal fluoro complexes in aqueous solution have been determined. However, there are very few reports in which the FIA determination of metal ions, or their influence on the response characteristics of the fluoride ion-selective electrode, based on metal fluoride complex formation are discussed [4][5][6][7].…”