USE OF REVERSED-PHASE LIQUID-CHROMATOGRAPHY FOR LIGANDS DETERMINATIONIN CU(II)-AMINO ACID COMPLEXES ADSORPTION STUDIES

Studies on metal-organic matter interactions in seawater and at the se diment-water interface are very important for evaluating the biogeoche mical cycles of trace metals in natural waters.(1) Adsorption of trace metals by clays, oxides, and other material appears to be an importan t means for controlling the soluble metal concentration in heterogeneo us systems.(2) Such adsorption seems to be controlled by the metal com plexes concentration and not by the ''free'' metal concentration. Usua lly, studies centered on adsorption of complexed metals deal only with the determination of the metal concentration.(2-6) However, the use o f suitable analytical procedures for the determination of the ligands provides useful and interesting information. In this study, besides th e metal amount, we determined the ligands in the solutions before and after contact with the solid phase, using a reversed phase-liquid chro matographic procedure that was optimized in this laboratory for the an alysis of amino acid and Cu-amino acid complexes.(7,8) In this case, R P-HPLC gives the opportunity not only to separate (in future these exp eriments could be repeated on a mixture of different amino acids) and to quantify the substances by means of its detection system, but even to utilize the information regarding retention order, i.e. the polarit y or hydrophobicity of the amino acid, in order to better confirm adso rption mechanisms. This work, which is part of a more extensive study on adsorption mechanisms in marine environment, describes the behaviou r and the effects of complex formation on the adsorption of copper fro m aqueous solutions by hydrous oxide surfaces (inorganic fractions of a marine sediment), simulating the solid/liquid proportion present in interstitial water, which has an important role in the early diagenesi s of various compounds in sediments, and, therefore, in the remobiliza tion of trace metals.