EVALUATION OF IMMOBILIZED METAL AFFINITY-CHROMATOGRAPHY (IMAC) FOR ISOLATION AND RECOVERY OF STRONG COPPER-COMPLEXING LIGANDS FROM MARINE WATERS

The speciation of dissolved copper in surface seawater is dominated by complexes with at least two classes of organic ligands, L-1 (the stro nger) and L-2 (the weaker). However, because these ligands have never been isolated, recovered, and characterized, their nature and identiti es are unknown. We have taken a combined approach utilizing immobilize d metal affinity chromatography (IMAC) for isolation, and copper titra tion monitored by differential pulse anodic stripping voltammetry (DPA SV) at a thin mercury film, rotating glassy carbon disk electrode for detection of these ligands in marine waters and in chromatographic fra ctions. We have found that, using the IMAC protocol reported by A.S. G ordon (Isolation of compounds with affinity for copper from seawater u sing immobilized copper ion affinity chromatography, Mar. Chem. 38 (19 92) 1-12), we can remove the majority of L-1 and L-2 from Chesapeake B ay and Atlantic coastal water samples. Once isolated, similar to 67% o f the L-1-class ligands bound to the IMAC column could be recovered by elution with 5 mM glycine buffer, as monitored by DPASV copper titrat ion of the column eluent. This recovery accounted for similar to 47% o f the original amount of L-1 in the sample and resulted in a 5.4-fold concentration factor (from 7 to 38 nM) of the ligands from the seawate r sample into glycine eluent. Although this IMAC protocol traps the we aker, L-2 class ligands as well as L-1 class ligands, confirmation of L-2's recovery by elution of the IMAC column is hindered by the presen ce of glycine in the eluent. We are currently devising procedures to o ptimize the isolation and improve recovery efficiency of IMAC for thes e ligands, in order to obtain sufficient quantities for further charac terization.