桑色素褪色光度法测定茶叶中的锰

锰是人体必需的微量元素,具有重要的生理功能和营养作用.茶树对锰有富集现象,茶叶是人们常用的饮料[1].因此,建立一种灵敏而又简便的测定痕量锰的分析方法,具有重要的实用价值.     

微乳液增敏测定微量锰

锰是人体必需的微量元素,它能促进人体的发育且具有抗癌作用[1]。缺锰会引起动脉硬化和癌症,过量锰会引起锰中毒,使中枢神经系统损害,直至语言障碍,因此,研究和建立高灵敏度的分析测定微量锰的方法具有重要意义。微乳液是由表面活性剂、助表面活性剂和水按适当比例组成的均匀的、透明的、各向同性的热力学稳定体系,与胶束体系比较,具有超低的介面张力和很高的增溶能力,在吸光光度法中日益得到应用[2-5]。本文研究了多种胶束及微乳液对水杨基荧光酮光度法测定锰的增敏作用。结果表明,CTMAB/正丁醇/正庚烷/水微乳液增敏作用最强,并测定了水…     

双波长双指示剂催化动力学光度法测定茶叶和水中微量锰北大核心CSCD

锰是人体必需的微量元素,人体缺锰会引起许多疾病,如早期胚胎发育不良,成人会引起高血压、肝炎、肝癌和衰老等病状,但锰过量也会引起中毒[1],因此研究食品、保健食品中痕量锰的测定具有重要的现实意义。目前,测定锰的催化动力学光度法已有许多报道[2-6],但大多采用单一指示剂在单波长下进行测定,灵敏度不够高,利用双波长双指示剂体系测定微量组分可提高灵敏度[7],     

双波长双指示剂催化动力学光度法测定茶叶和水中微量锰

<正>锰是人体必需的微量元素,人体缺锰会引起许多疾病,如早期胚胎发育不良,成人会引起高血压、肝炎、肝癌和衰老等病状,但锰过量也会引起中毒[1],因此研究食品、保健食品中痕量锰的测定具有重要的现实意义。目前,测定锰的催化动力学光度法已有许多报道[2-6],但大多采用单一指示剂在单波长下进行测定,灵敏度不够高,利用双波长双指示剂体系测定微量组分可提高灵敏度[7],但这种方法研     

在镍和溴化十六烷基三甲铵微乳液作用下二安替比林对溴苯基甲烷与锰(Ⅳ)的显色反应

１　引　言锰是人体生命活动中极为重要的微量元素，锰的摄入主要通过食物，因而准确测定食品中锰的含量具有重要意义。锰的测定常用高锰酸盐光度法，该法灵敏度较低。二安替比林苯基甲烷类试剂与锰（Ⅶ）的显色反应具有很高灵敏度，但稳定性和选择性不太好。为了提高该类型显色剂与锰显色反应的选择性，我们研究了在碱性介质中空气氧化锰（Ⅱ）为锰（Ⅳ）后，在镍和溴化十六烷基三甲铵（ＣＴＭＡＢ）微乳液协同作用下，锰（Ⅳ）与二安替比林对溴苯基甲烷（ＤＡｐＢＭ）的显色反应。体系选择性比ＤＡｐＢＭ与锰（Ⅶ）的显色反应有改善，方法…     

长寿金丹——锰

锰是人体不可缺少的微量元素。锰是丙酮酸脱羧酶的组成部分，也是许多酶系统的重要活化剂，它能促进、增强人体内许多重要的代谢反应。人体如缺锰，会导致生长发育障碍、身体矮小、瘦弱、智力下降、反应迟钝、贫血、面色苍白、无力以及共济失调、平衡障碍等中枢神经系统症状。由于锰参与人体内胆固醇的合成，而胆固醇是性激素的前体，所以缺锰可引起性激素缺乏，导致不育症。     

催化光度法测定井水和白葡萄酒中痕量锰

锰是人体必需的微量元素之一 ,适量的锰有利于身体健康 ,而含量过高或过低都会引起某些器官的病变而出现不适 ,因而准确测定痕量锰具有重要意义。锰的催化光度法测定已有不少报道 ,作者在试验中发现在乙酸 -乙酸钠介质中 ,锰对高碘酸钾氧化维多利亚蓝的褪色反应具有强烈催化作用 ,其褪色反应速率与 Mn( )的浓度在一定范围内呈良好的线性关系。本文研究了维多利亚蓝催化动力学光度法测定痕量锰的条件 ,建立了测定痕量 Mn( )的方法。方法检出限为 0 .1 3ng· ml-1,选择性较好。本法已用于井水和白葡萄酒中锰的测定。1　试验部分1 .1　仪器与…     

流动注射催化动力学光度法测定微量锰

在人体中的微量锰能促进发育,且具有抗癌作用,而锰的摄取,一般来自食物[1],如饮用水、茶叶、大米、豆类等,因此,测定环境样品中锰具有实际的意义[2-4].催化动力学光度法测定微量锰也有许多     

微量元素锰污染对人体的危害

介绍了微量元素锰污染的来源、毒性机理以及对人体的危害。慢性锰中毒主要表现为神经毒性、生殖毒性,锰也能引起肝脏、肺等脏器的损害。由于锰不能被生物降解,在环境中只能发生各种形态之间的转化,所以锰造成的污染消除很困难,对人体引起的影响和危害成为人们更为关注的问题。     

人体怎样补锰

缺锰可以引起多种疾病 ,但体内锰含量过高也不利于健康 ,如含量过高会发生锰中毒 ,还会损害中枢神经。锰在人体组织中总量只有 1 2～ 2 0毫克 ,人体对锰需要量并非很高 ,成人每天 5毫克就足够了。锰元素主要靠从食物中摄取 ,食物以坚果 (如核仁、栗子、松子等 )及粗粮、干豆含锰最多 ,其次是蔬菜、干果 ,水产品、鱼肝、鸡肝等锰含量也较高。在每日膳食中 ,若荤素兼备 ,人体就可摄食 5毫克锰 ,能满足人体对锰的需要。一般来说 ,动物性食品的锰较植物性食品易于吸收。需注意的是 ,进食动物性食品时 ,不要同吃菠菜 ,不要多喝茶 ,因为茶叶中鞣酸…     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.