Determination of NTA and EDTA and speciation of their metal complexes in aqueous solution by capillary electrophoresis

The interest in the use of chelates for enhancing metal uptake by plants du ring phytoremediation and their widespread use in plant nutrient research r equires that an easy, reproducible method be developed for chelate detectio n in a variety of systems. This work examined the use of capillary electrop horesis for chelate analysis. Electropherograms for nitrilotriacetic acid ( NTA) and ethylenediaminetetraacetic acid (EDTA) and their metal complexes w ere obtained by capillary electrophoresis in a phosphate buffer by direct U V detection at 185 nm. The metals used were Ca(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Pb(II), and Fe(III). For the majority of metals studied, l inear calibration curves were obtained in the concentration range of 10-100 0 mu M. The direct method of determination at 185 nm Was found to give a hi gher detection sensitivity than direct detection at 254 nm. Limits of detec tion for the metal chelate complexes were in the range of 2-50 mu M. The an alysis was fast (<6 min), exhibited low relative standard deviations for re tention time (<1%) and peak corrected area (<5%), and required no complex s ample pretreatment. The method was used to demonstrate speciation in comple x nutrient media.