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目录 1.前言···································································2 copyright paper51.com 2.实验部分·······························································2 内容来自www.paper51.com
2.1主要仪器和试剂······················································2 copyright paper51.com 2.2仪器主要工作条件····················································3 http://www.paper51.com 2.3实验方法与步骤······················································3 内容来自www.paper51.com 2.3.1标准曲线绘制····················································3 http://www.paper51.com 2.3.2试样的处理······················································4 http://www.paper51.com 2.3.2.1灰化处理·····················································4 paper51.com 2.3.2.2水浸处理·····················································4 paper51.com 3.结果与讨论·····························································5 内容来自www.paper51.com
3.1灰化后茶叶中铅测定··················································5 paper51.com 3.2茶叶水浸液中铅的测量················································7 内容来自www.paper51.com
3.3灰化后茶叶中间样中铅的测量·········································10 http://www.paper51.com 3.4加标回收测定·······················································11 内容来自www.paper51.com 3.5方法精密度与灵敏度················································12 http://www.paper51.com 4.结论··································································13 copyright paper51.com 5.致谢··································································13 内容来自www.paper51.com 参考文献································································14 paper51.com 1前言 内容来自论文无忧网 www.paper51.com
茶是中华民族的举国之饮。我国茶区之多，饮茶之盛，茶艺之精，也可称世界之最，素负盛名[1]。随着现代生活水平的提高以及茶饮料的普及，人们在探索茶叶作为保健饮品的同时，也开始把注意力集中在茶叶重金属污染、农药残留等食品卫生方面的问题。据相关资料报道，铅是人体不需要的，且过量时也对人体有害的重金属，铅含量高于2mg/kg即为超标[2]。Pb对人体有害，它在细胞内能与蛋白质的巯基结合，通过抑制磷酸化而影响能量的产生，以及抑制三磷酸腺苷酶而影响细胞膜的运输功能，从而使卟啉代谢紊乱，导致血红蛋白前血红素合成的障碍，它作用于全身各系统和器官，主要是神经、造血、消化、心血管系统及肾[7]。最近几年，关于茶叶中铅元素的测定、污染等方面的报道较少。加强这方面的研究，并严格控制，对提高茶叶质量和强化茶叶保健作用具有重大意义。本文对市面上销售的20种茶叶进行分类收集，试图对茶叶中铅含量和分布情况以及品种、等级等的关系作初步探讨。 paper51.com
2实验部分 内容来自www.paper51.com 2.1主要仪器和试剂 copyright paper51.com 主要仪器：S2-AA-SS型火焰原子吸收分光光度计、电子天平、可调式电炉、 马弗炉 内容来自论文无忧网 www.paper51.com
试剂：盐酸（AR）；硝酸（AR）；Pb标准储备液为市售国家标准溶液，浓度1000ug/mL，临用前稀释。 copyright paper51.com 茶叶试样：均为市售茶叶，品种分别为：1、云南沱茶（云南下关）；2、大益七子饼—普洱生茶（云南西双版纳）；3、大益七子饼—普洱熟茶（云南西双版纳）；4、临沧大雪山乔木饼茶—普洱生茶（云南临沧）；5、云南七子饼茶—普洱熟茶（云南临沧）；6、云南龙生普洱生茶（云南普洱）；7、云南龙生普洱熟茶（云南普洱）；8、红韵号圆茶—又一春（云南昆明）；9、云南凤凰沱茶（云南南涧）；10、景运野生古树茶（云南普洱）；11、云南普洱砖茶（云南昆明）；12、下关沱茶（云南下关）；13、下关特级沱茶（云南下关）；14、普洱沱茶（云南西双版纳）；15、大益普洱沱茶（云南西双版纳）；16、原味普之味（云南新平）；17、随心所欲迷你茶（云南新平）；18、小茶方砖（云南普洱）；19、普洱小沱茶（云南普洱）；20、陈香熟浓普之味（云南昆明） http://www.paper51.com |