DETERMINATION OF FREE NITRILOTRIACETIC ACID IN ENVIRONMENTAL WATER SAMPLES BY ION CHROMATOGRAPHY WITH POTENTIOMETRIC AND AMPEROMETRIC DETECTION WITH A COPPER ELECTRODE

An ion-chromatographic method is described for the analysis of free nitrilotriacetic acid in water samples. Separations are achieved on a polymer-based anion-exchange column with 6 mM nitric acid as eluent. Both potentiometric and amperometric detection have been applied using metallic copper as the indicator electrode. Detection limits are at about 500 ng injected in the potentiometric mode and 100 ng in the amperometric mode. On-line sample preconcentration is possible for volumes up to 2 ml of river water samples. The response of the detector to other aminopolycarboxylic and aminopolyphosphonic acids has been investigated.