Determination of ethylenediaminetetraacetic acid by flame atomic absorption spectrometry with a chelating ion-exchange flow injection conversion system

Abstract

A flow injection method (FI) has been developed for the determination of ethylenediaminetetraacetic acid (EDTA) by flame atomic absorption spectrometry (FAAS). In the first step a copper(II) regenerant solution was injected on to an on-line column packed with Chelex-100 resin. The excess of copper ion, not retained on the column, was washed by an ammonia solution carrier. In the second step an EDTA sample was injected. The analyte displaced an equivalent amount of copper(II) from the chelating column. Eluted copper was determined by an FAA spectrometric detector positioned downstream. The signal obtained was proportional to the concentration of EDTA present in the injected sample. Using this FI-FAAS conversion method the detection limit was 0.1 µg ml–1. The precision of the technique was better than a relative standard deviation of 1.5% at 0.50 µg ml–1 levels, with a throughput of 45 samples h–1. The effect of sample volume and of ionic and organic ligand interferents on the FI-FAAS signals was studied. Only glycylglycine was found to interfere significantly.