同时测定中草药中痕量铅和汞的氢化物原子荧光法

提出了同时测定痕量铅和汞的氢化物发生原子荧光法 ;采用断续流动氢化物发生器 ,以碱性铁氰化钾为氧化剂 ,在柠檬酸介质中产生铅烷和汞蒸气 ;讨论了氧化剂和络合剂对铅烷和汞蒸气生成的作用机理 ,考察了共存元素的干扰情况;在选定最佳工作条件下 ,测得铅和汞的检出限(3σ)分别为0.21μg·L-1 和0.026μg·L-1,相对标准偏差(对20μg·L-1Pb和2μg·L-1Hg,n=11)分别为1.2 %和0.71 % ;该法应用于中草药中痕量铅和汞的同时测定 ,结果令人满意     

CVG-ICP-AES法测定饮用天然矿泉水中痕量铅和汞

自制化学蒸气发生器并建立了KBrO3KBr K3Fe(CN)6HCl KBH4的CVG ICP AES同时直接测定饮用天然矿泉水中痕量铅和汞的方法,该方法提高了灵敏度,改善了检出限。方法的检出限分别为0.7μg·L-1(Pb220.353nm),0.1μg·L-1(Hg184.950nm),相对标准偏差分别为0.8%～7.8%(Pb)和0.5%～6.2%(Hg);回收率分别为90.0%～100.0%(Pb)和92.8%～108.0%(Hg)。方法完全能满足饮用天然矿泉水中痕量铅和汞的分析。     

离子色谱法测定微量碘的检测器应用研究

以NaOH为淋洗液 ,分别使用电导、直流安培和紫外检测器优化了碘的离子色谱分离和测定条件 ,检出限分别为 30 ,1和 2 5 μg·L- 1。选用安培检测法测定了奶粉中低于 10 0 μg·L- 1的微量碘 ,回收率达到 89.0 %     

邻菲咯啉荧光猝灭法测定粉丝中的铝

基于铝对邻菲罗啉的荧光具有猝灭的特性,拟定了一种测定痕量铝的新方法.该方法的激发波长为235nm,发射波长为366nm.线性范围为10μg·L-1～1.0mg·L-1,相关系数为0.9996,检测限为0.96μg·L-1,对于50μg·L-1的铝标准溶液测定10次的相对标准偏差为1.10%,用该方法测定了粉丝中的微量铝,结果令人满意.     

全固态铅离子选择性电极测定人发中微量铅

提出了用全固态铅离子选择性电极测定人发中微量铅的方法。在 1.5 g·L- 1抗坏血酸 1g·L- 1三乙烯四胺 0 .0 5mol·L- 1高氯酸钠 ,pH 4.85 .5的条件下 ,采用格氏作图法可准确测定人发中微量铅。方法简便、准确度高 ,回收率 95 % 10 6% ,相对标准偏差小于 5 .3 %。     

氢化物原子荧光光谱法测定食品中铅

研究了500 ℃干灰化法氢化物原子荧光光谱法测定食品中微量铅,在 15 g·L-1硼氢化钾还原剂介质和5 g·L-1氢氧化钾溶液中,样品溶液酸度以 0.24 mol·L-1盐酸为最佳。铅浓度在5~30μg·L-1范围内呈线性,相关系数为0.993 7。RSD小于10%,回收率为91%~104%。     

在线流动注射螯合树脂预富集石英缝管增敏火焰原子吸收法测定水中痕量镉和铜

应用高效的在线流动注射螯合树脂预富集石英缝管增敏火焰原子吸收系统直接测定水中痕量镉和铜 ,试验用内装 2 0 0 mg Amberlite XAD- 4键合的 5-磺酸 - 8-羟基喹啉螯合树脂的锥形柱 ,在 p H6条件下 ,样品流速为 6.0 ml·min-1,90 s装样 ,用 0 .5mol· L-1HCl洗脱 ,分析速度为30样·h-1分别获得 38和 40倍的富集 ,经石英缝管增敏 ,总灵敏度分别提高 1 36和 1 2 0倍 ,检出限为 0 .1和 0 .2μg· L-1。对镉和铜含量分别为 2 .0 ,5.0μg· L-1的水样连续测定 1 1次的相对标准偏差分别为 2 .8%和 3.4% ,可直接测定水体中 μg· L-1级的镉和铜。     

氢化物发生原子吸收光谱法测定食品中铅

采用微波溶样,以盐酸铁氰化钾硼氢化钾反应体系,将标准液及食品中铅氧化为Pb4+,利用连续流动注射氢化物发生器,以15g·L-1硼氢化钾在酸性条件下产生的氢自由基,与Pb4+生成的PbH4(铅烷)气体从反应体系中逸出,导入电热石英原子化器,采用高性能空心阴极灯作光源,进行原子吸收光谱检测。方法的灵敏度为0.065μg·L-1/1%A,检出限为0.070μg·L-1,线性范围在0～14μg·L-1之间,相关系数为0.9991,RSD小于3%,加标回收率为97%。     

Ru(Ⅲ)-CPA-DBC-KIO4褪色反应催化光度法测定微量钌

报道了以钌(Ⅲ)催化KIO4氧化CPA-DBC为基础的测定微量钌的催化光度分析,建立了一种在水相中直接测定微量钌的方法.钌(Ⅲ)含量在4.0～30.0μg·L-1范围内符合比耳定律,检出限为4.0μg·L-1.方法用于贵金属精矿中钌的测定,结果满意.     

微柱高效液相色谱法测定烟草样品中铁钴镍铜锌锰

研究了用2(2喹啉偶氮)5二甲氨基酚(QADMAP)为柱前衍生试剂,以Waters XterraTMRP18(1.0mm×50mm,2.5μm)微柱为固定相,72%的甲醇(内含0.5%的乙酸)为流动相,高效液相色谱法分离,二极管矩阵检测器检测测定铁、钴、镍、铜、锌和锰的方法。根据信噪比(S/N=3)得各金属离子的检出限分别为:铁3μg·L-1、钴和铜4μg·L-1、镍2μg·L-1、锌5μg·L-1、锰8μg·L-1,方法用于烟草中痕量铁、钴、镍、铜、锌和锰的测定,相对标准偏差在1.6%～3.8%之间,回收率在93%～107%之间,结果满意。     

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.     

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%).     

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.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

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.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.