Determination of rare earth elements by inductively coupled plasma-mass spectrometry after dispersive solid phase extraction with novel oxidized graphene oxide and optimization with response surface methodology and central composite design

A novel oxidized graphene oxide (OGO) material was prepared and employed for the dispersive solid phase extraction (d-SPE) of rare earth elements (REEs) in drinking water and nuts followed by inductively coupled plasma mass spectrometry (ICP-MS) determination. The novel material was characterized by Brunauer-Emmett-Teller (BET) surface area analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform-Infrared spectroscopy (FT-IR). Response Surface Methodology (RSM) with a Central Composite Design (CCD) and Derringer's type Desirability Function were employed for the optimization of factors that could possibly influence the extraction recovery. Response surfaces charts illustrated the effects of the examined parameters and their interactions. Under the optimum conditions, the detection limits ranged between 0.03 and 1.08 ng L-1 and the limits of quantification range between 0.09 and 3.26 ng L-1. The relative standard deviations for intra-day repeatability (concentration - 50 ng g t , n = = 5) and the inter-day repeatability (concentration = 50 ng g(-1) n = = 5 x 3) were 4.2-6.2% and 6.2-7.6%, respectively. The sample preparation procedure with the oxidized graphene oxide nanoparticles was simple and fast while it provided good enrichment factors and extraction recoveries. The method was successfully applied for the determination of trace REEs in almonds, peanuts and walnuts as well as tap and mineral water.