气相色谱法测定茶叶及土壤中的高效氯氟氰菊酯残留量

建立了气相色谱测定茶叶及土壤中高效氯氟氰菊酯残留量的分析方法。茶叶和土壤样品用正己烷提取,毛细管柱分离,气相色谱-电子捕获检测器(GC-ECD)检测。结果表明: 在高效氯氟氰菊酯添加量为0.02～2.00 mg/kg范围内,高效氯氟氰菊酯在鲜茶叶和土壤中的平均添加回收率分别为89.0%～94.1%和89.8%～94.7%,相对标准偏差(RSD, n=5)分别为3.0%～4.9%和2.5%～4.2%,方法的最低检出限(S/N=3)为0.002 mg/kg。采用该方法测定2.5%高效氯氟氰菊酯微乳剂在湖南长沙茶叶及土壤中的消解动态,其符合一级动力学消解模式,消解方程分别为y=3.1996e-0.3394x和y=0.1224e-0.1036x,相关系数分别为0.9956和0.9247。在茶叶中的半衰期为2.04 d,在土壤中的半衰期为6.69 d。该方法为湖南长沙地区茶叶种植科学合理地使用杀虫剂高效氯氟氰菊酯提供了依据。     

原子吸收和原子荧光光谱法测定茶园土壤中的微量元素

采用微波消解-火焰原子吸收和原子荧光光谱法同时测定了贵州梵净山茶园土壤中14种微量元素含量,方法简单、准确、迅速,有助于全面、迅速地了解茶园土壤中微量元素的含量,对于特色茶叶品质鉴定和指导合理科学栽培茶树等方面有重要意义.     

Substituent and solvent effects on the structural bioactivity and anticancer characteristic of catechin as a bioactive constituent of green tea

In this study, quantum chemical calculations using density functional theory and 6‐311G (d) basis set have been applied to analyze the substituent effect on the electronic structural properties including thermochemical parameters as well as anticancer characteristics of catechin as a bioactive constituent of green tea. It has been found out that different substituents with two kinds of electron donating and electron withdrawing groups including ? NO₂, ? NH₂, ? Cl, ? OCH₃, and ? CH₃ leaded to different structural stabilities. The catechin with chloro substituents has been referred to the most stable catechin derivatives based on the minimum energy of investigated compounds. In this study, the calculated values have been compared in gas phase and different solvent media with a wide range of solvent dielectrics using the self‐consistent reaction field method with polarizable continuum model. Relative interaction energies between solute and solvent as well as dipole moment values have been analyzed. The results of solvent effect study revealed that the formation of hydrogen bonds accounts for the stabilization of catechin. These calculated data were found to be a logical way in predicting the relative stability of catechin derivatives and can be useful for drug design of anticancer drugs and would open a new door for the researchers who are interested in natural products. The results presented in this article will be helpful to improve existing model and will open up a whole new arena of study to understand the anticancer characteristic of these antioxidant drugs derived from natural products against the photosensitizing DNA damage induce by catechin extracts and enable a much clearer understanding of how anticancer drugs mediate their effects on the specific spot. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

茶叶中锰、铁、锌、铬等10种微量元素的快速测定

茶叶样品经粉碎干燥后,以硝酸-高氯酸混合液进行消解处理,火焰原子吸收分光光度法测定了K、Ca、Na、Mg、Fe、Mn、Cu、Zn、Ni、Cr的含量。结果表明,回收率在89.30%～103.20%之间,相对标准偏差小于10%。方法简单、快速、经济,结果可靠。     

湖北绿茶中两种新的没食子酸类衍生物的结构鉴定

用2D NMR技术研究了从绿茶中分离得到的2种新的没食子酸类衍生物,对其¹H和¹³C NMR谱线作了全归属.     

Sensitive and selective determination of gallic acid in green tea samples based on an electrochemical platform of poly(melamine) film

In this work, an electrochemical sensor coupled with an effective flow-injection amperometry (FIA) system is developed, targeting the determination of gallic acid (GA) in a mild neutral condition, in contrast to the existing electrochemical methods. The sensor is based on a thin electroactive poly(melamine) film immobilized on a pre-anodized screen-printed carbon electrode (SPCE*/PME). The characteristics of the sensing surface are well-characterized by field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and surface water contact angle experiments. The proposed assay exhibits a wide linear response to GA in both pH 3 and pH 7.0 phosphate buffer solutions (PBS) under the optimized flow-injection amperometry. The detection limit (S/N = 3) is 0.076 μM and 0.21 μM in the pH 3 and pH 7 solutions, respectively. A relative standard deviation (RSD) of 3.9% is obtained for 57 successive measurements of 50 μM GA in pH 7 solutions. Interference studies indicate that some inorganic salts, catechol, caffeine and ascorbic acid do not interfere with the GA assay. The interference effects from some orthodiphenolic compounds are also investigated. The proposed method and a conventional Folin–Ciocalteu method are applied to detect GA in green tea samples using the standard addition method, and satisfactory spiked recoveries are obtained.     

龙井茶特征香气成分分析及种类判别

采用顶空固相微萃取(HS-SPME)和气相色谱-质谱(GC-MS)联用技术分析了39份龙井茶叶中的挥发性成分,结合质谱数据库与保留指数,从24份西湖核心区龙井茶中获得了200余种挥发性化合物,这些挥发性成分中主要含有醇类、酯类、酮类、杂环类等化合物,经筛选得到26种共有组分.并采用主成分分析法(PCA)对24份西湖核心区龙井茶和15份疑似龙井茶进行了有效区分.该方法适用于茶叶的品质鉴定、真假识别、产地溯源等方面的研究,也为其他产品的挥发性成分分析提供参考.     

Synthesis of phosphates and phosphates-acetates hybrids of green tea polyphenol (−)-epigallocatechine-3-gallate (EGCG) and its G ring deoxy analogs as potential anticancer prodrugs

A series of phosphate or phosphate-acetate hybrid modified EGCG or EGCG G ring deoxy analogs were synthesized by a convenient semi-synthesis strategy from the abundant natural compound EGCG.     

采用实时直接分析质谱法原位快速鉴别茶叶

采用近年来发展迅速的常温常压离子化技术——实时直接分析质谱法,建立了对茶叶中主要成分如茶氨酸、咖啡碱等的快速测定方法,通过特征的质谱信号离子,实现了对不同茶叶的快速鉴别。实时直接分析质谱法在大气压下进行,无需对茶叶进行任何的样品处理,大大缩短了分析时间,实现了原位、快速、准确且高通量的检测。     

气相色谱-串联质谱法测定茶叶中88种农药残留量

采用气相色谱-串联质谱(GC-MS/MS)分析技术,建立了高灵敏度检测茶叶中88种农药残留量的方法。目标化合物经加速溶剂萃取(ASE), Carb/NH2净化小柱净化,乙腈-甲苯(3:1, v/v)洗脱,采用GC-MS/MS测定。对方法的准确性、精密度、线性范围、最低检出限(LOD)和定量限(LOQ)进行了测试。其中87.5%的农药在低水平(6.4 μg/kg)的加标回收率为70%～100%; 87.5%的农药的相对标准偏差(RSD)小于15%。每个化合物均采用灵敏度最高的离子对进行定量,并采用空白茶叶基质配制标准工作液。LOQ以10倍信噪比(S/N=10)计算,86.4%农药的LOQ值低于10 μg/kg。该方法灵敏度高、准确、可靠,适用于绿茶、乌龙茶、红茶以及普洱茶中多种农药残留量的检测。