Titanium dioxide nanotubes as solid-phase extraction adsorbent for on-line preconcentration and determination of trace rare earth elements by inductively coupled plasma mass spectrometry

In this work, a novel method was developed for the determination of trace rare earth elements in biological and environmental samples by inductively coupled plasma mass spectrometry (ICP-MS) after on-line preconcentration/separation with a titanium dioxide nanotube packed microcolumn. The adsorption behaviors of the analytes on titanium dioxide nanotubes were studied systematically. The effects of the experimental parameters, including pH, sample solution flow rate and volume, eluent concentration and volume and interfering ions, on the recoveries of the analytes were examined in detail. Under the optimum conditions, the detection limits of this method ranged from 0.19 pg mL− 1 (Lu) to 1.2 pg mL− 1 (La) with an enrichment factor of 100, and the relative standard deviations (RSDs) for the determination of REEs were less than 5.0% (n = 9, c = 1.0 ng mL− 1). The linear range of calibration curve spanned three orders of magnitude. This method was validated using a certified reference material of tea leaves, and successfully applied for the determination of trace light (La and Ce), medium (Eu and Gd) and heavy (Lu and Yb) rare earth elements in real samples with recoveries of 95.5-103%.