Atomic Absorption Detector for Liquid-Liquid Chromatography

Abstract

A detector system specific for the measurement of chelating agents and applicable to liquid-liquid chromatography has been developed. A solution containing the chelating agent is passed over a short column of chelating ion exchange resin in the copper form, and directly into the aspirator of a recording atomic absorption spectrophotometer set to measure copper. A quantity of copper proportional to the quantity of the chelating agent is stripped from the column and recorded as a peak. Precision and accuracy compare with normal atomic absorption techniques, with an average mean standard deviation of 3%, and a corresponding accuracy. The detection limit for this method is 5x10-⁷ millimoles of EDTA or NTA. Determinations are rapid and reproducible in solutions having a pH in the range of 4 to 9. The role of interfering ions is considered. The applicability of the method as a specific detector system for liquid-liquid chromatographic separations of chelating agents is discussed. Recovery of chelating agents from solutions with an ionic strength approximating natural fresh waters is demonstrated.