Dual dispersive extraction combined with electrothermal vaporization inductively coupled plasma mass spectrometry for determination of trace REEs in water and sediment samples

Abstract

A simple and efficient two-step method based on dispersive solid phase extraction (D-SPE) and dispersive liquid–liquid microextraction (DLLME) has been developed for the separation and preconcentration of 15 rare earth elements (REEs) from environmental water and sediment samples, followed by electrothermal vaporization-inductively coupled plasma mass spectrometry (ETV-ICP-MS) detection. With Chelex 100 as the adsorbent of D-SPE, target REEs were firstly extracted and the retained REEs were then desorbed by 0.1 mol L⁻¹ HNO₃. After 125 mmol L⁻¹ Tris and 40 mmol L⁻¹ 1-phenyl-3-methyl-4-benzoylpyrazolone (PMBP) were added into the above elution solution, target REEs were further preconcentrated into CCl₄ by DLLME. The developed dual extraction technique exhibited high enrichment factors (234 to 566-fold) and good anti-interference ability. Various parameters affecting the extraction of target REEs by D-SPE and DLLME were investigated in detail. Under the optimal conditions, the limits of detection (LODs, 3σ) for target REEs were in the range of 0.003–0.073 ng L⁻¹ with the relative standard deviations (C_{Y,La,Ce,Pr,Nd,Gd,Dy} = 1.0 ng L⁻¹, C_{Sm,Eu,Tb,Ho,Er,Tm,Yb,Lu} = 0.2 ng L⁻¹, n = 7) ranging from 6.7 to 11.5%. The proposed method of D-SPE-DLLME-ETV-ICP-MS was successfully applied to the determination of 15 REEs in water and sediment samples with the recoveries of 78–115% and 75–117% for the spiked water and sediment samples, respectively. To validate the accuracy of the method, a Certified Reference Material of GBW07301a stream sediment was analyzed and the determined values were in good agreement with the certified values.