Determination of Ethyleneamines Using Flow Injection Analysis after Complexation with Cu(II)

A simple method based on a flow injection analysis is proposed for measuring the total concentration of ethyleneamines, including ethylenediamine (EDA), diethylenetriamine, triethylenetetetramine, and tetraethylenepentamine, as a concentration of EDA. A solution for measurement is prepared by adding 0.5 mL of 0.1 mol L^–1 acetic acid/sodium acetate buffer (pH 5) to 9 mL of a sample solution and diluting to 10 mL with deionized water; 150 μL of the solution is injected into a carrier stream (deionized water, 0.8 mL min^–1), and it is then mixed with 1 mmol L^–1 Cu(II) solution as a reagent solution (0.8 mL min^–1) in a reaction coil (0.5 m). The absorption of the formed complexes of the ethyleneamines with Cu(II) is measured at 242 nm. The calibration curve prepared using EDA showed good linearity up to at least 1.0 mmol L^–1; the limit of detection (S/N = 3) was 6.9 μmol L^–1 as the concentration of EDA in the sample solution. The reduction of interference by coexisting substances, such as compounds with absorption in the ultraviolet region, heavy metal ions, and compounds that can complex with heavy metal ions, was also investigated. The proposed method was applicable to the analysis of wastewater.