Solid-phase extraction of ethyleneamines in river water prior to their determination by high-performance liquid...

A method based on solid-phase extraction (SPE) has been developed for the preconcentration of three kinds of ethyleneamines (EAs) [ethylenediamine (EDA), diethylenetriamine (DETA), and triethylenetetramine (TETA)] in river water for their high-performance liquid chromatographic (HPLC) determination by using on-line complexation with Cu(II) ion and ultraviolet (UV) detection. EAs, which are protonated in acidic and neutral conditions, could be concentrated by using cation-exchange SPE. However, inorganic cations and humic substances, often present in river water, interfered with this preconcentration. Inorganic cations, such as Ca and Mg ions, compete with EAs in cation-exchange processes. This interference could be reduced by masking them with ethylenediaminetetraacetic acid. Humic substances, such as humic acid and fluvic acid, seem to be due to the electrostatic interaction of EAs with them in the sample solution. This interference was reduced by passing the sample solution through an anion-exchange cartridge before the cation-exchange SPE. The interacted EAs remained in the anion-exchange cartridge; they could be eluted by washing out the anion-exchange cartridge with diluted HCl. In this washing process, although fulvic acid was eluted at the same time, it could be removed by passing the eluate through a reversed-phase cartridge connected in a series. After removing these interferences, EAs could be extraced with the cation-exchange SPE and quantitatively eluted by passing Cu(II) solution through the cartridge. The proposed method of including the HPLC-UV combined with the SPE was available for the determination of EAs in river water at concentrations as low as 0.015 µM for EDA and DETA and 0.05 µM for TETA. The high recoveries (83%-103%) and repeatabilities (RSD 1.2%-4.3%) were obtained for EAs from two river water samples spiked with two different concentrations of EAs. The proposed method was applied to analyses of river water samples taken from four rivers in Toyama Prefecture, Japan.