La, Ce, Pr, Nd and Sm concentrations in Puʹer tea of Yunnan, China

The rare earth elements contents (La, Ce, Pr, Nd, Sm) in 150 Puʹer tea samples were analyzed by using inductively coupled plasma atomic emission spectroscopy (ICP-AES), to evaluate the safety of Puʹer tea. Among the investigated rare earth elements (REEs), Ce was the highest (35% of the total REEs content) whose concentrations were found to be in the range of 0.11-1.39 mg/kg, whereas that of Sm in the range 0.01-0.21 mg/kg, showing minimum levels (5.2%). La was the second highest element (28%) found in Puʹer tea samples, followed by Nd (24%) and Pr (7.7%). The concentration of La was in the range of 0.07-1.14 mg/kg while that of Nd and Pr were in the range of 0.01-1.17 mg/kg and 0.01-0.30 mg/kg, respectively. The contents of La, Ce and Nd in ripened Puʹer tea were significantly higher than those in raw Puʹer tea. There were significant differences on the distribution of La, Ce, Pr, Nd and Sm in Puʹer tea among the main producing areas. Based upon the present Chinese quality safety standards, 43% samples in this study were found to be unsafe for human consumption.