Lietuvos mokslų akademijos Leidybos skyrius
    Tel. +370 5 2626851, +370 5 2613620 El. paštas leidyba@lma.lt
Chemija / Chemistry

ISSN 0235-7216
ISSN 2424-4538 (online)

2009 m. Nr. 3

Investigation of electrode kinetics and thermodynamics of [Zn–L-amino acidate–vitamin B7] complexes by voltammetric technique
Farid KHAN, Afroza KHANAM

The voltammetric reduction of Zn2+ using L-lysine, L-ornithine, L-threonine, L-serine, Lphenylglycine, L-phenylalanine, L-glutamic acid, L-aspartic acid and vitamin B7 (biotin) at pH 7.30 ± 0.01 and I = 1.0 M NaClO4 was reported at 25 and 35 °C. The nature of the current voltage curves was quasireversible and diffusion-controlled. Zn2+ formed 1 : 1 : 1, 1 : 1 : 2 and 1 : 2 : 1 complexes with these drugs as confirmed by the Schaap and McMaster method. The sequence of the stability constant of L-lysine < L-ornithine < L-threonine < L-serine < L-phenylglycine < L-phenylalanine < L-glutamic acid < L-aspartic acid complexes can be explained on the basis of the size, basicity and steric hindrance of ligands. The values of the stability constant (log β) varied from 2.13 to 11.37 and confirm that these drugs, i. e. L-amino acids or in combination with vitamin B7 or their complexes, could be used against Zn2+ toxicity. The thermodynamic parameters such as enthalpy (ΔH), free energy (ΔG) and entropy change (ΔS), are also reported. The kinetic parameters viz. the transfer coefficient (α), degree of irreversibility (λ), diffusion coefficient (D) and standard rate constant (k) were calculated. The values of α confirmed the symmetric nature of the ‘activated complex’ between oxidants and reductants in response to the applied potential between the dropping mercury electrode and solution interface.

Keywords: voltammetry, thermodynamic parameters, electrode kinetics, [Zn–L-amino acidate–vitamin B7] complexes

Issues:

2017 - Vol.28
No. 1, No. 2, No. 3, No. 4

2016 - Vol.27
No. 1, No. 2, No. 3, No. 4

2015 - Vol.26
No. 1, No. 2, No. 3, No. 4

2014 - Vol.25
No. 1, No. 2, No. 3, No. 4

2013 - Vol.24
No. 1, No. 2, No. 3, No. 4

2012 - Vol.23
No. 1, No. 2, No. 3, No. 4

2011 - Vol.22
No. 1, No. 2, No. 3, No. 4

2010 - Vol.21
No. 1, No. 2-4

2009 - Vol.20
No. 1, No. 2, No. 3, No. 4

2008 - Vol.19
No. 1, No. 2, No. 3-4

2007 - Vol.18
No. 1, No. 2, No. 3, No. 4

2006 - Vol.17
No. 1, No. 2-3, No. 4

2005 - Vol.16
No. 1, No. 2, No. 3-4

2004 - Vol.15
No. 1, No. 2, No. 3, No. 4

2003 - Vol.14
No. 1, No. 2, No. 3, No. 4

2002 - Vol.13
No. 1, No. 2, No. 3, No. 4

2001 - Vol.12
No. 1, No. 2, No. 3, No. 4