DETERMINATION OF EDTA, NTA, AND OTHER AMINO CARBOXYLIC-ACIDS AND THEIR CO(II) AND CO(III) COMPLEXES BY CAPILLARY ELECTROPHORESIS

EDTA and NTA were widely used in the processing of nuclear materials a nd in the production of nuclear energy. Their in-plant chemical transf ormations and post-disposal chemical and biological transformations ge nerated many additional amino carboxylic acid compounds. Toxic and rad ioactive metals are frequent co-contaminants of these chelating agents . Some of the resulting metal ion-chelating agent complexes, most nota bly (60)Co(III)EDTA, resist decomposition and adsorb poorly onto subsu rface minerals, thereby facilitating migration. This study sought to s eparate and detect free amino carboxylic acids and their Co(ll) and Co (lll) complexes in a single run without prior pretreatment using capil lary electrophoresis (CE). The electrolyte filling the CE capillary co ntained 25 mM phosphate buffer (pH 7). Equilibrium calculations perfor med for this electrolyte identified predominant cobalt species and hel ped explain the CE findings. Co(lll) complexes are thermodynamically ( and kinetically) more stable than corresponding Co(ll) complexes and a re readily separated and detected. Co(lll) complexes of EDTA, NTA, and IDA were synthesized and analyzed. Two different diastereomers of Co( III)IDA(2) were found and could be separated. Co(ll)-amino carboxylate complexes range from ones that are not thermodynamically stable in th e capillary and therefore not detectable to those that are highly stab le in the capillary and yield good linearity.