Study of solid-phase extraction for the determination of sequestering agents in river water by high-performance liquid chromatography

Anion-exchange solid-phase extraction accompanied with high-performance liquid chromatography has been developed for the determination of six kinds of aminopolycarboxylic acids (APCAs) in river water [N-(2-hydroxyethyl)ethylenediaminetriacetate (HEDTA), ethylenediaminetetraacetate (EDTA), 1,3-propanediaminetetraacetate (PDTA), diethylenetriaminepentaacetate (DTPA), 1,2-propanediaminetetraacetate (MeEDTA), and O,O′-bis(2-aminoethyl)ethyleneglycoltetraacetate (GEDTA)]. The enrichment of APCAs using an anion-exchange cartridge was successfully done by the removal of anions, which competed with APCAs in anion-exchange processes. Barium chloride solution was added to river water and the mixture was passed through On Guard II Ag and H cartridges and then a Bond Elut Jr.SAX cartridge to enrich APCAs. After elution, APCAs were analyzed on two reversed phase C30 columns connected in series and detected with ultraviolet detection. The enrichment using solid-phase extraction permitted the determination of APCAs in river water at concentrations as low as 1 nM. Good recoveries (83–111%) were obtained for each APCA by the standard addition method on three river water samples with high accuracy (RSD 1.8–9.5%). Applying this method, two kinds of APCAs, EDTA and DTPA, were determined in samples from the Oyabe and Senbo Rivers in Japan.