Determination of hydroxy-2-ethylenediaminetriacetic acid (HEEDTA) and Fe-HEEDTA in nutrient solutions by ion-pair reversed-phase high-performance liquid chromatography

A reversed-phase ion-pair liquid chromatography method for the accurate det ection and determination of hydroxy-2-ethylenediaminetriacetic acid (HEEDTA ) and Fe-HEEDTA has been developed. Three mobile phases containing 0.05 hi tetrabutylammonium hydroxide, 0.05 M tetrabutylammonium bromide, or 0.05 M tetrabutylammonium bromide + phosphate buffer were employed in this method. Iron was added to each mobile phase after addition of the selected ion pai r reagent to determine the amount of HEEDTA in both the free and/or the met al chelated forms at concentrations as low as 50 mu M. The method depends o n the formation of the iron chelate with HEEDTA in the mobile phase at pH 7 . Calculation of the amounts of chelated HEEDTA with iron in the mobile pha se was verified using the Geochem-PC computer program, which showed that 99 .95% of HEEDTA was chelated to iron at pH 7. (C) 1998 Academic Press.