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A model of non‐nernstian response in the determination of aluminum ions by indirect potentiometry
Author(s) -
Ngila J. Catherine,
Alexander Peter W.,
Hibbert D. Brynn
Publication year - 1995
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.1140071007
Subject(s) - ionic strength , chemistry , protonation , aluminium , fluoride , ion , analytical chemistry (journal) , acetic acid , electrode , dispersion (optics) , inorganic chemistry , aqueous solution , chromatography , biochemistry , physics , organic chemistry , optics
Flow analysis data of the response of an aluminum wire electrode to fluoride into which Al 3+ is added is modeled assuming a logarithmic response of the electrode to F − and reaction of F − with aluminum ions to give a series of complexes [AlF q ] (3− q )+ 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 m (OH) n ] (3 m − n )+ when m = 1, n = 1,2,3,4; m = 2, n = 2; m = 3, n = 4; m = 13, n = 32, and the acetate complex [Al 2 (OH) 2 OAc] 3+ . Protonation of F − to HF and HF 2 −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.