茶叶中铅的初级形态分布

Primary Speciation Analysis of Lead in Tea

研究茶叶形态提取的最佳条件:提取时间为15h,3h,3h和3h;提取温度为35℃,提取溶剂用量50mL.并在此条件下,选取5种铅总量梯度茶叶作为研究对象,对各形态含量进行测定,结果表明,同一品种茶叶(龙井43,福建龙井)由于铅总量的不同,导致各形态铅的浸提率差异很大;而相同地方不同品种茶叶(龙井43,石佛香)虽然铅总量略有差距,但形态分布较为接近.茶叶中铅的形态分布规律为,盐酸提取物>醋酸提取物>乙醇提取物>水提取物>氯化钠提取物,盐酸提取和醋酸提取物中铅含量之和占茶叶中铅总含量47.78%-70.30%,剩余部分的铅以更加稳定的形态存在于残渣中.茶叶中能够被人体吸收的铅所占比例很小.

With 80% C2H5OH,H2O,1mol/L NaCl,2% CH3COOH,0.6 mol/L HCl as the extract solvents respectively,the primary speciation analysis of Pb in tea sample was performed.By single factor experiments the optimal extraction time for these solvent was 15h,3h,3h,3h respectively.The optimal extraction temperature was 35℃ and extraction volume was 50 mL each time.Five tea samples were used for the speciation analysis of Pb.The results showed that among the same variety of the tea the distribution of Pb-compound was quite different.There is a little difference for the Pb content among of several tea samples from the same region,and little difference with the existing form of Pb.For all the tea samples,the extracted efficiency is different with solvents,i.e.HClHACC2H5OHH2ONaCl.The total amount of the HCl extraction and HAC extraction was about 47.78%-70.30%.The residual Pb compound exists in tea with a much stable form.The ratio of the Pb to be intaken easily by human body was very lower.