Detection of aluminum-citrate-phosphate ternary complexes in aqueous solution by 27Al and 31P NMR

Akiko Yamaguchi, Yutaka Tsuji, Shuqin Bai, Yoshihiro Okaue, Takushi Yokoyama

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Abstract

In order to confirm the formation of ternary aluminum-citrate-phosphate complexes, which have been predicted by a potentiometric study on the reaction between aluminum ion, citrate and phosphate in aqueous solution, 27Al and 31P NMR spectra for solutions containing aluminum ion (Al) citrate (L) and phosphate (P) {Al : L : P mole ratio 1 : 1 : n (n = 0 ∼?5)} at pH 3.0 and 4.0 were measured. In a solution of pH 3.0 with Al : L = 1 : 1 in the absence of P, a mononuclear Al-L complex in addition to [Al(H 2O)6]3+ existed, while in a solution with Al : L : P = 1 : 1 : 1 of the same pH, the formation of a ternary complex (P-Al-L) was confirmed by 27Al and 31P NMR measurements. The broad 27Al and 31P NMR peaks assigned to the P-Al-L were observed around 0 ppm and -4.8 ppm, respectively. The intensity of both peaks increased with increasing the proportion of P. In a solution with the same composition of pH 4.0, the formation of a trinuclear complex, (Al 3-L3), the major species in the solution with Al : L = 1 : 1 in the absence of P, was prevented due to the predominant formation of the P-Al-L.

Original languageEnglish
Pages (from-to)185-189
Number of pages5
Journalbunseki kagaku
Volume56
Issue number3
DOIs
Publication statusPublished - Aug 20 2007

All Science Journal Classification (ASJC) codes

  • Analytical Chemistry

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