对甲苯磺酸三乙铵作为气相色谱固定相测定酱油中的苯甲酸

苯甲酸具有杀灭或抑制微生物繁殖的作用,其作为食品防腐剂,被广泛用于酱油、罐头、酱菜以及饮料等食品中。但摄入过量的苯甲酸会影响人体的肝脏功能,对人体产生危害,因此食品中苯甲酸的测定一直受到人们的关注。用于测定食品中苯甲酸的气相色谱固定相有许多,比如SE-30[1]、DEGS     

吹扫捕集-气相色谱-质谱法测定生活用水及塑料水管中20种挥发性有机物的含量北大核心CSCD

近年来,随着工业污染的加重,挥发性有机物(VOCs)已成为水体常见污染物之一[1]。VOCs具有迁移性、持久性和毒性[2],若长期饮用含VOCs的水将严重损害人体健康,会对人体免疫系统、中枢神经系统和一些内脏器官等产生毒害作用,因此其被列为优先控制污染物[3-5]。     

4-氨基安替比林紫外分光光度法测定肉与肉制品中亚硝酸根

亚硝酸根是含氮化合物分解过程中的中间产物,其分解的亚硝基极易与肌红蛋白反应生成具有致癌作用的亚硝基肌红蛋白,从而对人体造成危害,是肉与肉制品中必检测的指标之一.亚硝酸根测定方法,文献报道的方法有国标法[1]、动力学分光光度法[2]、荧光分析法[3]等.本研究发现在盐酸介质中,亚硝酸盐和4-氨基安替比林反应,反应产物溶液在310 nm波长处有特征紫外吸收,据此建立测定亚硝酸根的方法.方法应用于肉与肉制品中亚硝酸根的测定,操作简便,结果满意可靠.     

利用压电频移分析法测定硫

1　引言硫是人体必需的元素之一,也是蛋白质等许多具有生物活性物质的重要组成元素。硫与人体健康的关系十分密切,硫的医疗价值越来越引起人们的重视,因此硫的测定具有重要意义。对于硫离子的测定,提出了包括极谱分析法[1]、电位分析法[2]、分光光度法[3]等多种分析方法。...     

绝色谱法快速测定食品中苯甲酸（钠）和山梨酸（钾）

许多食品中常需加入一定量的苯甲酸 (钠 )或山梨酸 (钾 )作为防腐剂 ,但此类防腐剂的过量加入 ,会对人体产生危害[1] ,,对苯甲酸 (钠 )和山梨酸 (钾 )的测定方法有薄层色谱法、气相色谱法、高效液相色谱法、紫外分光光度法、酸碱滴定法及硫代巴比妥酸比色法等[2 ] 。本文根据混合物的各成分性质和结构上的不同 ,在滤纸上固定相和流动相间产生的吸附作用不同[3] ,这种物理化学现象的差异 ,用纸色谱法对食品中苯甲酸 (钠 )和山梨酸 (钾 )进行了测定。1　试验部分1.1　试剂苯甲酸 (钠 )、山梨酸 (钾 )、苯甲酸 (钠 )和山梨酸(钾 )混合标准溶液 …     

铅锌对烟草复合污染程度的分析

随着工农业的发展,越来越多的污染物进入环境中共存并发生着复杂的相互作用[1]。因此对多种污染物相互作用形成的复合污染效应的研究已成为环境科学研究的重要方向[2-7]。其中重金属由于难以被生物降解,并可通过食物链富集,危害人体健康,而成为当今世界普遍关注的环境问题之一。在重金属污染中,铅污染的来源广泛,而且铅是毒性较大的重金属之一,因此铅对环境的污染尤为突出。锌是植物微量营养元素,同时也是环境污染元素。一些研究报道了Pb-Zn共存条件下二者的环境生态效应。如秦天才等[8]探讨了Pb-Zn复合污染对小白菜根系的生理生态效应,结…     

湿法消解-氢化物发生-原子荧光光谱法同时测定中药材中硒和铋的含量

正中药材种类繁多,组成复杂,既含有有机组分又含有丰富的微量元素,有部分微量元素是危害人类身体健康的有毒、有害元素,也有部分微量元素具有药效作用,是中药的有效成分之一。因此,在提高中药质量方面不仅需要有效控制中药材的有机活性成分,同时也必须对中药材中直接关系到人体健康的微量元素含量进行准确地测定和控制[1]。硒是人体必需的微量元素之一,被科学家称为人体微量元素中的"抗癌之王",其参与维持人体正     

石墨炉原子吸收光谱法测定水溶性食品添加剂中铅的含量

正食品添加剂是指为改善食品的色、香、味,以及为防腐、保鲜和加工工艺的需要而加入食品中的人工合成或者天然物质,食品添加剂不应对人体健康产生任何危害[1]。铅或重金属作为有害物质,会对人体产生危害,因此很多食品添加剂标准将其作为限量指标[2-5]。不同种类的食品添加剂对这一限量指标规定的测定方法也不同,目视比色法容易受到     

气质联用法测定饮用水中29种挥发性有机物

挥发性有机物(VOCs)具有高挥发性、类脂物可溶性、易被皮肤、粘膜吸收等特点,对环境和人体有较大的影响和危害.新<生活饮用水卫生标准>(GB/T 5749-2006)[1]中VOCs的检测项目从原来的2项增加到25项.顶空气相色谱是过去测定水中VOCs的常用方法,但该法灵敏度较低,不适于数十种挥发性有机物同时检测[2].新技术吹扫捕集-气质联用法(P&T-GC-MS)能同时分析测定多种物质,前处理方式也较简便,因此成为测定水中VOCs的推荐方法[3-6].     

重氮偶联光度法测定痕量亚硝酸盐

作为当前化学学科的前沿之一,绿色化学的研究与应用已受到广泛关注[1,2]。绿色化学的目标是从源头上防止污染的发生,而这一目标的实现离不开绿色分析化学。亚硝酸盐是典型的污染物,是自然界中氮循环的中间产物,广泛存在于环境和食品中。人体摄入一定量的亚硝酸盐可发生高铁血红     

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.