Free Access
Volume 28, Number 2, March 2000
New trends in material science
Page(s) 127 - 131
Section Original articles
Analusis 28, 127-131 (2000)
DOI: 10.1051/analusis:2000104

Influence of the ligand concentration and pH on the complexation of Cu(II) by a soil fulvic acid

A.I. Herrero1, E. Barrado1, F. Rey1, 2 and A.A.S.C. Machado3

1  Departamento de Química Analítica, Facultad de Ciencias, Universidad de Valladolid, Spain
2  Permanent address: Area de Química Física, Universidad de Vigo, Torrecedeira 86, E-36208 Vigo, Spain
3  LAQUIPAI, Faculdade de Ciencias, Universidade de Porto, Portugal

(Received February 5, 1999; revised February 8, 2000; accepted February 22, 2000.)

Anodic Stripping Voltammetry has been tested in a non-traditional, pH-variable procedure, to study the interaction between Cu(II) with a soil fulvic acid. The study was performed at 25 °C and I = 1.0 M, and covered wide ranges of fulvic acid concentration ( $5 - 20~{\rm mg}~{\rm L}^{-1}$), Cu(II) concentration ( 2.10-5-4.10-6 M), and pH (3.5 - ca 8). Mean complexation equivalent weights (between 800 and 5000 g mol-1, depending of experimental conditions) and apparent equilibrium constants (between ca. 3 and 0.02 for pH-independent constants), and their variations with pH and fulvic acid concentration were calculated through an iterative procedure. The results obtained are consistent with those published before for the implementation of the pH-variable procedure with Cu(II) ion selective electrode potentiometry, and show that Anodic Stripping Voltammetry at pH-variable conditions is suitable for the study of Cu(II) - fulvic acid interactions.

Key words: Fulvic acid -- Cu(II) complexation -- Anodic Stripping Voltammetry.

© EDP Sciences, Wiley-VCH 2000