快速测定水样中的硝酸盐和亚硝酸盐

1 引言 测定硝酸盐的常用比色法有酚二磺酸法和紫外双波长法，但这两者都有一定的缺陷。N-（1-萘基）-乙二胺盐酸盐光度法是一种测定亚硝酸盐的简便、准确的方法，为国内外普遍采用。由于亚硝酸盐和硝酸盐在近紫外区的吸收光谱有重叠而影响硝酸盐在紫外区的测定。去除亚硝酸盐干扰的方法有2种，一种是通过加入氨基磺酸来消除，另一种是先测出亚硝酸盐的浓度，通过校正曲线算出它在紫外区的吸光度，再从总吸光度中扣除，其中后一种方法更合理。但笔者依据后一种思想测定硝酸盐和亚硝酸盐的混合溶液中的硝酸盐含量都较理论值低，而通过多元线性回归方程计算的硝酸盐值比单独用硝酸盐标准曲线计算的结果更好。     

一阶导数分光光度法直接测定肉制品中硝酸盐及亚硝酸盐的含量

本文研究了硝酸盐及亚硝酸盐的一阶导数光谱，选择亚硝酸盐的一阶导数光谱与基线相交点２０７ｎｍ，作为硝酸盐的测定波长；选择硝酸盐在２０７ｎｍ、２２０ｎｍ处导数值相等，作为双波长法测定亚硝酸盐的测定波长。结果表明，硝酸盐及亚硝酸盐在１～１５μｇ／ｍＬ浓度范围内线性关系良好，合成样分析，加标回收试验，样品测定同标准比色法对照均获得满意结果。     

紫外分光光度法测定蔬菜鲜样中的硝酸盐

建立了紫外分光光度法测定蔬菜鲜样中硝酸盐含量的方法，经t检验证明，该方法的测定结果与酚二磺酸法无显著性差异，RSD小于4．5％，方法操作简便，适用于蔬菜中硝酸盐含量的测定。     

紫外吸光光度法测定蔬菜鲜样中硝酸盐氮

采用紫外吸光光度法测定蔬菜鲜样中硝酸盐含量，该法适用于不同硝酸盐含量的蔬菜样品测定，与传统的酚二磺酸法相比，该法精密度和准确度高、操作简便，具有较大的推广价值。     

光化学动力学法测定硝酸盐和亚硝酸盐

本文研究了甲基橙动力学法测定水、食品及蔬菜中硝酸盐和亚硝酸盐。在紫外光照射下甲基橙退色程度与硝酸盐和亚硝酸盐含量成正比。文中提出首先测定二者的总量,然后在氨基磺酸存在下测定硝酸盐的量,再差减求得亚硝酸盐的量。     

稀土与穴醚[2,1,1]配位反应过程中的阴离子重排现象

用电导法研究了甲醇溶液中稀土硝酸盐及氯化物与穴醚［２，１，１］的配位作用，测定了１：１配合物的稳定常数ｌｇＫ及摩尔电导ΛＭＬ。在甲醇溶液中，稀土氯化物与［２，１，１］配合物的稳定性大于硝酸盐的相应配合物。稀土硝酸盐与［２，１，１］配合物的稳定常数ｌｇＫ随镧系收缩有明显的钆断效应。电导测定表明，在甲醇溶液中，稀土硝酸盐为弱电解质。轻稀土与［２，１，１］反应后为１：１型电解质，重稀土配合物则属１：２型电解质；稀土氯化物在甲醇中为１：１型电解质，所形成的配合物均为１：２型电解质。     

硫酸肼还原NEDD光度法测定地表水中硝酸盐氮

硝酸盐氮的浓度是水质调查的必测项目.目前水质监测分析中硝酸盐氮的测定常用酚二磺酸法和镉柱还原、偶氮染料显色光度法,方法手续都较繁复.本法在原田泰和北村等人工作的基础上,用铜、锌溶液催化、硫酸肼还原、偶氮染料显色,光度法测定地表水中硝酸盐氮,操作简便,结果满意.     

大气中单个硝酸盐和硫酸盐颗粒的测定方法

介绍一种测定大气中单个硝酸盐和硫酸盐颗粒的方法，在采用复合薄膜法确定了单个硝酸盐和硫酸盐颗粒的基础上，再利用X射线能谱仪对它们进行元素分析，其中，颗粒中所含的硝酸根离子和硫酸根离子分别由反应生成的针状结晶物和圆环状结晶物来确定，而对应的阳离子则由X射线能谱仪检出，在实验室中对12种大气中常见的硝酸盐和硫酸盐人工颗粒和实际大气颗粒物进行了观察，结果表明该法是可行的。     

离子色谱法测定火腿中的硝酸盐和亚硝酸盐

建立了离子色谱分离-电导检测法测定火腿中的亚硝酸盐和硝酸盐的分析方法。样品经粉碎、溶剂沉淀除蛋白和固相萃取净化后,采用优化后的色谱条件测定。结果表明,硝酸盐和亚硝酸盐浓度分别在0.02-0.5mg/L和0.2-5mg/L内具有良好的线性关系,方法回收率92.8-98.2%。该方法检测这两种离子测定简便,稳定,满足火腿中硝酸盐和亚硝酸盐含量的同时测定。     

乙二胺合钴溶液中亚硝酸盐和硝酸盐氮的测定

建立了快速测定乙二胺合钴溶液中亚硝酸和硝酸盐的方法。使用麝香草酚法测定硝酸盐,使用改进了的GB 13580.7-92测定亚硝酸盐。硝酸盐的线性范围在8 mg·L-1以内,亚硝酸盐的线性范围为0.03~0.8 mg·L-1,相关系数分别为0.999 9,0.999 4。硝酸盐的加标回收率在99.9%~108%之间,测定值的相对标准偏差(n=7)为1.2%;亚硝酸盐的加标回收率在99.5%~107%之间,测定值的相对标准偏差(n=7)为1.4%。     

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.