Determination of ultratrace rare earth elements in tea by inductively coupled plasma mass spectrometry with microwave digestion and AG50W-x8 cation exchange chromatography

Abstract

The concentration of ultratrace rare earth elements (REEs) in tea was accurately determined by inductively coupled plasma mass spectrometry (ICP-MS), based on microwave digestion for sample preparation and AG50W-x8 cation-exchange chromatography for separation of REEs from the matrix. The spectroscopic interferences of matrix-induced polyatomic ions BaO⁺, BaOH⁺ with Eu⁺ were eliminated. The application potential of the method was evaluated by analysis of Certified Reference Materials of Tea (GSV-4) and Bush Twin Leaf (GSV-2). A good agreement between the results and certified values was observed. The recoveries of spiked samples for each REE were from 90 to 105% with a precision of <9% RSD. Very low levels of procedure blanks were maintained from 0.007 to 0.6 ng cm^–3. The limits of detection (LOD) were between 0.0039 and 0.0003 ng cm^–3 for REEs in solution. The results suggested that the developed method was very effective for the determination of REEs in tea. The levels of REEs in naturally grown teas were low but foreign REEs could accumulate in tea.