云南省保山市不同茶叶中重金属浸出特征分析

Analysis on Leaching Characteristics of Heavy Metals in Tea from Yunnan Baoshan

采用ICP-MS法对产自云南省保山市的绿茶、红茶、普洱生茶、普洱熟茶及其茶汤中重金属(As,Cd,Cr,Ni和Pb)质量分数进行分析,研究茶叶在不同冲泡次数、冲泡时间、冲泡温度下重金属的浸出规律.结果表明,供试茶叶样品中As,Cd,Cr和Pb的质量分数远低于国家卫生质量标准的最高质量分数限定值,但各重金属质量分数差异较大,表现为:w(Ni)>>w(Cr)≈w(Pb)≈w(As)>>w(Cd).茶汤中重金属浸出率随冲泡次数的增加而降低;随浸泡时间延长而增大,浸泡30 min后增幅平缓,浸出量基本稳定;同时,浸出率随浸泡温度的升高而增大,80℃以上恒温浸泡重金属浸出量增幅明显.茶叶中Ni和Pb较易浸出,Cd较难浸出.

In order to study the leaching rule of five heavy metals（ Al,Cd,Cr,Ni and Pb） from tea to tea infusions,ICP-MS were used to analyze green tea,black tea,Pu＇er raw tea and Pu＇er ripe tea from Baoshan,Yunnan at first. Then the tea infusions brewed by three key factors（ Number of brewing,brewing time and brewing temperature） were analyzed. The results showed that the quality mass contents of As,Cd,Cr and Pb were far below the limited value of national standards,respectively. Each heavy metal showed the quality mass content difference which could be expressed as： w（ Ni） 〉〉w（ Cr） ≈w（ Pb） ≈w（ As）〉〉 w（ Cd） in all the samples. Heavy metals in tea infusions decreased with increasing of the numbers of brewing. The contents of those elements increased with immersion times,and the upward trends slowed down after 30 min,which indicated the leaching rate became steadily. The leaching rate increased with the water temperature increasing and it became obvious when the temperature reached to above 80 ℃ and Ni and Pb in tea were easier to leach than Cd.