Determination of complex forming ability of mixed-ligand organic systems relative to the metal ions
Abstract
It is shown that classical and specific methods for determining the complex forming ability of mixed-ligand organic systems relative to the metal ions is not perfect. Determination of complex-forming ability of mixed-ligand organic systems relative to the metal ions using the method of turbidimetry for media containing biometal chlorides, mixed-ligand systems and sodium carbonate is proposed. As mixed-ligand systems used the culture fluid Bifidobacterium bifidum AC-1670 (mixed-ligand system I), the culture fluid of the composition of probiotic bacteria (mixed-ligand system II), the culture fluid of the composition of probiotic bacteria with the introduction of exogenous chelating agents (mixed-ligand system III), culture fluid of probiotic bacteria composition and products of their cell walls processing (mixed-ligand system IV). A solution of metal chloride (magnesium or calcium, or cuprum, or manganese, or ferrum or zinc) was added discretely to the aliquots of the solution of the organic mixed-ligand system. The mixture was stirred and kept for 30 minutes at 40 °C, then a solution of sodium carbonate was added to the aliquots and discretely measured turbidity of the solution by turbidimetric method at a wavelength of 450 nm. When the increasing of the turbidity magnitude system by 0.02 opt. un, a conclusion about the maximum value of the mixed-ligand organic systems complex forming capacity relative to the metal ion was made. Further increase in the turbidity of the system indicates an increase in the metal content in inorganic form, respectively the complex formation potential of the mixed-ligand system is exhausted. It is determined that the highest complex forming ability in relation to ions of biometals has mixed-ligand system III. The proposed method allows precisely to determine the complex formation capacity of mixed-ligand organic systems in relation to metal ions without the use of aggressive reagents capable of destroying chelate bonds and without involving high-cost rare equipment.
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