SEPARATION AND QUANTITATION OF SOME METAL-IONS BY RP-HPLC USING EDTA AS COMPLEXING AGENT IN MOBILE-PHASE

Ion pair reversed-phase high performance liquid chromatography has been used to achieve the simultaneous separation of some transition metal ions including Ni(II), Co(II), Cu(II), Mn(II), Fe(III), Pb(II), Cr(III), and Hg(II) as complexes of ethylenediaminetetraacetic acid (EDTA) originated, in the column itself. Due to the negative charge of the metal complexes, the separation of metal ions from inorganic anions such as Cr2O72- and NO3- is possible by employing a positively charged counterion in the mobile phase. The influence of the nature and concentration of counterion, organic modifier content, ionic strength, EDTA concentration and pH of the mobile phase on the retention and selectivity has been investigated. Quantitation of metal ions was achieved with spectrophotometric detection. Detection limits ranged from 300 pg for Fe(III) to 35 ng for Cr(III) with a linearity of 2-3 orders of magnitude. Some applications of the technique to the separation of multielement mixtures are shown.