Fast Determination of Rare Earth Elements in Tea Samples by ICP-MS with Modified Oxygen Flask Combustion

A new method for accurate determination of 15 rare earth elements including Y-Lu in tea samples by inductively coupled plasma. mass spectrometry(ICP-MS) was proposed. Sample preparation was based on the modified oxygen flask combustion technique. By using quartz cloth coated with glycerol instead of filter paper as the ignition agent, a total amount of 0. 1 g sample could be completely burned in a 500-mL flask. Key factors affecting the sample preparation effect were systematically investigated, and it was found that the extraction efficiencies of over 90% for all the analytes could be realized with 5 mL of 4% HNO3 + 1% HF (V/V) as the extractant for the combustion residue and the total extraction process could be finished in one minute under sonication, which resulted in a very fast sample preparation procedure that could be completed in less than 3 minutes. The relative standard deviations (RSD) of six parallel determination values were between 2. 7% and 5. 5%, and the detection limits ranged from 0. 001 mg/kg to 0. 006 mg/kg. Three tea standard reference materials were analyzed with the method and the detection results agreed well with the standard values. The method was successfully applied to three real samples analysis.