Cu(II)–amino acid and Cu(II)–peptide chelates in animal feeding: a semi-quantitative approach to characterize the commercial products and the limits of their structural integrity

Abstract

The paper describes an analytical procedure to assay the quality of commercial amino acid/peptide-based metal chelates used in animal feeds. In order to characterize the hydrolyzed protein mixture alone or in the commercial product, a semi-quantitative approach based on size exclusion chromatography, amino acid and peptide HPLC analysis and acid base titrations were used. The interference caused by the copper ions in the HPLC analysis of the complexes was eliminated by a previous exhaustive electrolysis removing this metal ion from the solution. Moreover, circular dichroism experiments were used to test the degree of hydrolysis of the starting protein and to furnish direct information on the quality of the commercial product.