Electrochemical characterization of iron(III)-glycine-nitrilotriacetate mixed ligand complexes and their stability in aqueous solutions

Cuculić, Vlado; Pižeta, Ivanka (2006) Electrochemical characterization of iron(III)-glycine-nitrilotriacetate mixed ligand complexes and their stability in aqueous solutions. Croatica Chemica Acta, 79 (1). pp. 41-48. ISSN 0011-1643

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Abstract

Electrochemical characterization of iron(III)-glycine-nitrilotriacetate (iron(Ill)-Gly-NTA) mixed ligand complexes and determination of their stability constants and retention time in aqueous solutions (I = 0.1 mol dm(-3) in NaClO4, pH = 8.0 +/- 0.1 at 25 +/- 1 degrees C), using differential pulse cathodic voltammetry (DPCV), cyclic voltammetry (CV) and direct current (d.c.) polarography with a static mercury drop electrode (SMDE), were performed. Iron(Ill) concentrations were varied from 5x10(-6) to 6x10(-4) mol dm(-3), NTA total concentrations varied from 2x10(-5) to 1x10(-3) mol dm(-3) and glycine total concentrations were 0.2, 0.02 and 0.002 mol dm(-3). lron(Ill) redox reaction in the mixed ligand system (by the techniques employed) was found to be a one-electron reversible process. At total concentration ratios of I : 800 : 2 for iron(III), glycine and NTA, respectively, the iron(Ill)-Gly-NTA mixed ligand complexes were dissolved and stable (> 18 hours) in the aqueous solution. The complexes were formed either by the addition of NTA into the iron(111) and glycine aqueous solution or by the addition of iron(111) to the mixture of glycine and NTA. Under these conditions, iron(III) hydrolysis was highly suppressed. By fitting of experimental data, the following stability constants for mixed ligand complexes, not found in the literature so far, in 0.1 mol dm(-3) NaClO4 aqueous solution were calculated: for iron(111) log beta(1)([FeGlyNTA](-)) = 27.23 +/- 0.69, log beta(2)([Fe(Gly)(2)NTA](2-)) = 30.29 +/- 0.77; for iron(II) log beta(1)([FeGlyNTA](2-)) = 14.13 +/- 0.43 and log beta(2)([Fe(Gly)(2)NTA](3-)) 18.51 +/- 0.51.

Item Type:

Article

Uncontrolled Keywords:

iron(III); mixed ligand complexes; nitrilotriacetate (NTA); glycine; stability constants; voltammetry; aqueous solution ; stripping voltammetry; electrode-reactions; crystal-structure; iron hydrolysis; water solution; trace-metals; iron(iii); phytoplankton; acids; constants

Subjects:

NATURAL SCIENCES > Chemistry

Divisions:

Division for Marine and Enviromental Research

Projects: