Methyl benzoate as a non-halogenated extraction solvent for dispersive liquid–liquid microextraction: Application to the preconcentration of copper(ii) with 1-nitroso-2-naphthol

Abstract

Methyl benzoate, whose density is greater than that of water, was used as a non-halogenated extraction solvent for dispersive liquid–liquid microextraction (DLLME). The quantitative extraction of some elements, such as Au(III), Cd(II), Co(II), Fe(III), Ni(II), Pb(II), and Pd(II), was achieved using some traditional extractants, including diethyldithiocarbamate, 1-(2-pyridilazo)-2-naphthol, 8-hydroxyquinoline, and 1-nitroso-2-naphthol (NN) with acetone as a disperser solvent. As a demonstration, the preconcentration of Cu(II) with NN was studied in detail. The Cu(II) in 8 mL of a sample solution was rapidly and quantitatively extracted at pH 7 using 80 μL of methyl benzoate containing 1 mmol L⁻¹ of NN; in this system, no disperser solvent was needed. After centrifugation, the extracted Cu(II) in a sedimented phase could be determined by electrothermal atomic absorption spectrometry. The detection limit was 2.3 ng L⁻¹ (three times the standard deviation of the blank values, n = 8) as the Cu(II) concentration in 8 mL of the sample solution. The proposed method was applicable to the determination of Cu(II) in some water samples, including tap water, ground water, and snow-melted water without any interference.