A new method for simultaneous determination of trace amounts of Cu(II) and Ni(II) ions by preconcentration and spectrophotometric analysis

Abstract

Immediate preconcentration and spectrophotometric methods have been developed for the determination of trace amounts of cupric ion (Cu(II)) and nickel ion (Ni(II)) through a solid phase extraction with XAD-4-N,N'-bis-(salicylidene) cyclohexanediamine (XAD-4-SCHD) resin and a complex color reaction of the ions with 2,6-dimethyl-morpholine dithiocarbamate (DMMDTC) in Triton X-100 media. A high preconcentration factor of 125 was achieved. The spectrophotometric method was based on the measurements of the absorption of colored chelates of ions complexing with DMMDTC, and the adsorptions of the complex solutions were measured at their maximum absorption peaks at 460 and 328 nm for Cu(II) and Ni(II) ions, respectively. The impact of the complexing reaction variables including type and amount of surfactant, pH, amount of ligand, and complexation time on the sensitivity of the proposed method was optimized. Calibration graphs were found to be linear in the ranges of 0.02-3 and 0.02-2.5 mg L−1 with detection limits of 5 and 7 μg L−1 for Cu(II) and Ni(II), respectively. The accuracy of the developed method was calculated by recovering all Cu(II) and Ni(II) ions in synthetic and TMDA-70.2 certified reference water samples. Results of the proposed method were also compared with inductively coupled plasma-mass spectrometry results for the determination of trace Cu(II) and Ni(II) ions in water samples.