茶叶中稀土元素的组成及存在状态

Composition and Existing State of Rare Earth Elements in Tea

用ＩＣＰＭＳ分析了安徽省郎溪茶场的茶叶及茶园土壤中的稀土元素含量、组成及存在状态。结果表明：茶叶中含有其栽培土壤中所有的１５种稀土元素，其中以Ｌａ、Ｃｅ、Ｎｄ、Ｐｒ和Ｙ为主，这５种元素含量之和占稀土总量的９２％。茶叶中和土壤中的稀土元素在组成和分布模式上基本相同，只是茶叶对Ｌａ吸收相对较多，而对Ｃｅ、Ｙｂ吸收相对较少而已。茶叶中的稀土元素四分之三以上是不溶于热水而残存在茶渣中，其中又有１６％是与α纤维素结合在一起的，因此，人们喝茶时摄入的稀土元素不足茶叶中稀土含量的四分之一（约０４８ｍｇ／ｋｇ，远低于≤２０ｍｇ／ｋｇ的国家允许标准）。茶叶中存在有稀土多糖复合物，茶汤中约有８％的稀土是以这种状态存在的。在稀土多糖中以Ｌａ、Ｃｅ、Ｎｄ为主，其含量约占８０％以上。

The content, composition and exiting state of rare earth elements (REEs) in tea garden soil from Lanxi Tea Estate of Anhui Province were studied with ICP-MS method. Results showed that there were the same 15 REEs in tea as that in tea garden soil, with La, Ce, Nd, Pr and Y as the major elements and the total content of these 5 elements reached 92%. REEs in tea was similar in composition and in distribution pattern to that in the soil, however, tea plant absorbs more La than Ce and Yb from the soil. About over three quarters of the REEs in tea were insoluble in tea infusion and remained in tea residue, 16% of which was in combination with α-cellulose. The amount of REEs intaked in tea drinking was less than about 0 48mg/kg, quarter of REEs in tea, much less than 2 0mg/kg which is the maximum limits of state standard. REEs binding polysaccharides in tea was found and about 8% of REEs in tea infusion existed in this state. Over 80% REEs in REEs-binded polysaccharides in tea infusion were La, Ce and Nd.