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

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, 3 sigma) 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.