双波长分光光度法提高测定灵敏度的规律探讨

双波长分光光度法作为分光光度法的一个新的重要分支,正在受到人们的重视。在单组份测定中,选择络合物吸收峰波长作为测量波长,显色剂吸收峰波长作为参比波长的双波长分光光度法有利于提高测定的灵敏度,为简明起见,称为双峰双波长法。实验表明,以二甲苯胺蓝Ⅱ作为镁的显色剂,采用双峰双波长法比通常分光光度法的灵敏度约高三倍,而以双羧基偶氮胂Ⅲ作为稀土的显色剂仅提高灵敏度一倍左右。因此,探讨提高测定灵敏度的一般规律,从理论上指导双波长法的实际应用是有意义的。     

用单波长仪器代替双波长仪器进行测定的精密度研究——Ⅱ.双波长等吸收法测定双组分体系

目前,在国内双波长分光光度法的应用日趋广泛,在单波长仪器上完成测定者亦不在少数。前文就单波长仪器用于双波长分光光度单组分测定的精密度作了研究及论述。对于双组分或存在干扰组分时通常应用双波长等吸收法测定,本文拟对这种情况下的双波长测定精密度作一研究。 (一)精密度公式的推导及研究由双波长分光光度法原理得     

K系数—多波长最小一乘回归分光光度法同时测定三组分的研究

将双波长Ｋ系分光光度法和多波长线性回归分光光度法相结合，并采用最小一乘法准则计算回归系数，提出了一种同时测定三组分的新方法，即Ｋ系数－多波长最小一乘回归分光光度法。     

双波长-微分分光光度法的基础和应用

前言B.Chance 在1951年研制了双波长分光光度计(dual or two-Wavelength spectrophotometer),长期以来,为生物化学领域提供了独特的数据,但是一直没有普及。其原因一方面是因为仪器本身不是谁都能马上操作的,这和叫做线粒体计的仪器类似;另一方面是由于使用的范围非常狭窄。但对一般的研究人员来讲,双波长分光光度法的原理是容易理解的。1968年,日本研制成了商品化的双波长分光光度计,作者们尝试把双波长分光光度法应用于分析化学领域,自从在混合成分相互定量、微分分光光度法和高     

硫氰酸盐双波长分光光度法测定钨尾矿中微量钨

硫氰酸盐分光光度法测定钨,选择性较好且快速简便。但试样含硅太高时,酸化后易析出硅酸,限制了碱分解法的测定下限。鉴于双波长分光光度法对混浊液仍可测量的特点,我们采用硫氰酸盐双波长分光光度法,可以适当多称样,分取量大,允许少量硅酸     

XO-CTMAB胶束增溶双波长分光光度法同时测定轻重稀土

关于轻重稀土的分组测定,已有评述。近年来报导的较好的稀士分组显色剂,如偶氮氯膦mN及对乙酰基偶氮胂均为轻稀土显色剂。最近应用胶束增溶双波长分光光度法测定钇基稀土中的重稀土。应用胶束增溶双波长分光光度法同时测定轻重稀土尚未见报导。胶束增溶分光光度法与双波长法相结合,既能提高测定灵敏度,又可以提高方法的选择性,效果是显而易见的。基于以上考虑,有可能应用胶束增溶双波长法同时测定轻重稀土。鉴于稀土-二甲酚橙-表面活性剂体系测定     

双波长分光光度法原理简介

如所周知,分光光度法已是广泛应用着的一种分析方法。但是,采用经典的分光光度法时,对于多组份混合物的分别定量,必须解联立方程式,这不仅手续比较繁杂,计算麻烦,测定误差也较大。对于混浊试样或其他背景吸收大的试样的测定,经典的分光光度法则往往表现得无能为力。自从五十年代提出双波长分光光度法以来,随着双波长分光光度计的使用,上述问题便迎刃而解,并且大大提高了方法的灵敏度和选择性,     

质量控制分析中选择测定波长对的一种计算机程序

在双波长分光光度法中,用计算机选择波长对进行测定,可以获得较好的精确度,这方面已进行了不少工作。作者引入“权系数法”提出一种计算机选择测定波长对的新程序,其中考虑到了仪器测定偏差对测定结果的影响,以波长对的权系数为判据,可选出较为可靠的测定波长对。原理对于双波长分光光度法来说,仪器测定     

用二乙胺二硫代甲酸钠测定Cu(Ⅱ)和Bi(Ⅲ)的新萃取光度法

解联立方程法是分光光度法中测定多组分最常用的方法。采用双波长分光光度计,通过波长的适当选择,可以消除共存干扰组分的影响,大大简化了混合物同时测定的手续及其数据处理,并可提高测定的灵敏度和准确度。但是,目前双波长分光光度计甚少,根据双波长系数倍率法原理,我们研究了用单波长分光光度计同时测定相互干扰组分的新方法——倍     

双波长分光光度法测定混合组分

双波长分光光度法测定单组分,倘若以显色试剂吸收峰为参比波长,配合物吸收峰为测量波长(即双峰双波长法)可显著提高灵敏度,将该法用於混合组分体系的测定还未见报导。本文对双波长分光光度法测定混合干扰体系进行了研究,导出了双波长分光光度线性方程,对轻、重稀土-二甲酚橙-CTMAB体系及钴、镍-PAR体系进行了测定,采用直线回归及最小二乘两种方法处理实验数据。理论及实验均表明,采用此法测定混合组分体系,灵敏度较通常的单波长测定法有所提高。     

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.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

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.