Labile metals column elution

Adamic and Bartak [6] used high pressure aqueous size exclusion chromatography with reverse pulse amperometric detection to separate copper(II) complexes of poly(amino carboxylic acids), catechol and fulvic acids. The commercially available size exclusion chromatography columns were tested. Columns were eluted with copper(II) complexes of poly(aminocarboxylic acids), citric acids, catechol and water derived fulvic acid. The eluent contained copper(II) to prevent dissociation of the labile metal complexes. Reverse pulse electrochemical measurements were made to minimise oxygen interferences at the detector. Resolution of a mixture of DTP A, EDTA and NTA copper complexes was approximately the same on one size exclusion chromatography column as on Sephadex... 

Besides non-size exclusion effects, dilutions of the sample constituents during fractionation may lead to the dissociation of the labile complexes and thus affect the distribution of the metal. In order to reduce this problem some authors (Evans et al., 1978 and Yoza, 1977) have advocated the addition of a constant level of the metal or ligand in the buffer used to elute the sample from the column. This Is not a very useful approach since even if the buffer does not form strong complexes with the free ion added new species may be introduced. The only sensible approach is to minimise dilution. 

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