Solid Phase Extraction of Rare Earth Elements in Deep Groundwater With Multi-wall Carbon Nanotubes as Adsorbent for the Determination by Inductively Coupled Plasma Mass Spectrometry

A solid phase preconcentration method has been developed using hydroxyl multi-wall carbon nanotubes (MWNTs) as the absorbent. The method was optimized for the determination of rare earth elements (REEs) in deep groundwater samples by inductively coupled plasma mass spectrometry (ICP-MS). The effects of the experimental parameters, including pH, eluent concentration and volume, flow rates of sample and eluent solutions, and the sample volume on the recoveries of the analytes were examined in detail. Under optimum conditions, REEs can be quantitatively retained by MWNTs when the pH exceeds 3.0 and are then eluted completely with 1% HNO3. The detection limits of this method ranged from 0.31 ng L-1 to 1.2 ng L-1 and the relative standard deviations (RSDs) were less than 5%. The method was validated using a certified reference material and was applied for the determination of REEs in deep groundwater samples with satisfactory results.