Study of complexes of cadmium with some L-amino acids and vitamin-C by voltammetric technique

Abstract

Abstract:Voltammetric technique was used to study the binary and ternary complexes of cadmium with L-amino acids and vitamin-C (L-ascorbic acid) at pH =7.30 ± 0.01, µ = 1.0M KNO 3 at 25ºC and 35ºC. Cd (II) formed 1:1:1, 1:1:2 and 1:2:1 complexes with L-lysine, L-ornithine, L-threonine, L-serine, L-phenylglycine, L-phenylalanine, L-glutamic acid and L-aspartic acid used as primary ligands and L-ascorbic acid used as secondary ligand. The trend of stability constant of complexes was Llysine < L-ornithine < L-threonine < L-serine < L-phenylglycine < L-phenylalanine < L-glutamic acid < L-aspartic acid which can be explained on the basis of size, basicity and steric hindrance of ligands. The values of stability constant (log β) varied from 2.23 to11.33 confirm that these drugs i.e. L-amino acids or in combination with L-ascorbic acid or their complexes could be used against Cd (II) toxicity. The study has been carried out at 35ºC also to determine the thermodynamic parameters such as enthalpy change (∆H), Free energy change (∆G) and entropy change (∆S) respectively.

Mononuclear Binary Complex Formation Equilibria of L-Ornithine with Biologically Essential Metals in TBAB Micellar Media

“…L-Ornithine (L-Orn) is a non-protein 2,5-diaminopentanoic acid whose metal complexes are insoluble in water and soluble in most organic solvents [9]. It is a tridentate ligand [10,11] and known to form several stable metal ion complexes in a variety of solvents differing in the degree of solubility: with Co(II), Ni(II) and Cu(II) [12][13][14][15][16][17][18][19][20][21][22]; Cd(II), Sn(IV), Ce(IV) and Pd(II) in different solvents [23][24][25][26][27]. L-Ornithine complexes of bio-essential metals play an important role in chemotherapeutic applications [28,29].…”

Voltammetric method for the quantification of cadmium using non-commercial electrodes and minimal instrumentation

“…Although voltammetry is cheaper than other methods of instrumental analysis, commercial instrumentation for its development is inaccessible for many laboratories of low economic resources. Some researchers have shown that construction of instrumentation for electrochemical methods is possible, from selective electrodes 12,13 to potentiostats [14][15][16] .…”

Construction and Metrological Characterization of a Minimal Instrumentation Micropolarograph

“…The simultaneous quantification and the possibility of further speciation are some of the potentialities of the linear sweep voltammetric method. The determination of the number of electrons involved in an electrochemical reaction, the diffusion coefficient, the stability constants of coordination compounds, and the calculation of thermodynamic magnitudes are also possible [1,3,4]. It also allows, from the analysis of the voltammograms, establishing working conditions for the development of other electrochemical analysis methods, such as potentiometry, amperometry, and others.…”

“…Although its price is lower than other equipment for instrumental analysis, such as spectrophotometers, even the potentiostats are inaccessible to many laboratories. Other authors have reported research results using non-commercial equipment for the development of voltammetry methods [4,6,7].…”