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Voltammetric determination of the stability constants of copper(II) complexes with folic acid
Author(s) -
Maali Nagwa Abo El,
Ghandour Mahmoud A.,
Vire JeanClaude,
Patriarche Gaston J.
Publication year - 1989
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.1140010410
Subject(s) - chemistry , polarography , copper , protonation , stability constants of complexes , inorganic chemistry , anodic stripping voltammetry , stoichiometry , oxalic acid , voltammetry , ion , electrochemistry , organic chemistry , electrode
Both differential pulse polarography (DPP) and differential pulse anodic stripping voltammetry (DPASV) have been applied to the determination of the conditional stability constants of copper(II)‐folic acid complexes. The polarographic technique does not allow the investigation of these reactions in neutral media due to the interference of a hydroxy copper complex. DPASV exhibits two complexes with 1:1 and 1:3 stoichiometry at pH 7.4. The addition of 2 mM phosphate buffer affects the complexation mechanism; three different species are formed. In a weakly acidic medium (pH 4.5), only one complex is evidenced, but, due to the protonation of the pterin moiety of folic acid, which is the active site for complexation, an increase of the proton concentration inhibits the complex formation. Copper(II) ions are shown to be more strongly complexed than lead and cadmium ions under the same conditions. Using d.p.a.s.v. Copper(II) can be determined over the 4 × 10 −6 to 2 × 10 −5 M concentration range in the presence of 5 × 10 −6 M folic acid.