萘相萃取吸光光度法测定微量锌

5—Br—PADAP是一灵敏的金属显色剂,用5—Br—PADAP测定金属锌已有不少报道。本文用萘作为萃取剂,固—液分离Zn(Ⅱ)—5—Br—PADAP,对萘相分离物用乙醇—丙酮混合溶剂溶解,试验表明,Zn(Ⅱ)—5—Br—PADAP络合物能被萘相完全萃取,Zn(Ⅱ)在0～5.0μg/7ml范围内符合比耳定律,建立萘相萃取吸光光度法。该络合物最大吸收峰λ_(max)=555nm,表观摩尔吸光系数为1.23×10~5。本法灵敏度高,操作简便、快速,用于食品、水样中锌的测定,结果满意。     

双波长光度法同时测定水中微量铁和铜

提出了以5 Br PADAP为显色剂,在pH3.0的缓冲溶液中,用双波长光度法同时测定=590.水中微量铁和铜的最佳条件。选择的测定铁和铜的波长对分别为λFe1=503.5nm,λFe2=555.0nm,服从比耳定律的线性范围和检出限分别为0～16μg/25ml和0nm,λCu1=604.0nm,λCu20～24μg/25ml,0.008和0.006μg·ml-1,加标回收率分别为89.2%～105.4%和88.4%～102.0%。通过测定不同的水样,结果满意。     

卡尔曼滤波析相光度法同时测定锌、锰、镉──2-(5-溴-2-吡啶偶氮)-5-二乙氨基苯酚-Triton X-100体系

1引言析相光度法具有富集和分离作用，已用于一些微量元素测定．本文运用卡尔曼波波递推法，以2－（5一摸一2一毗峻仍氛）七一二乙氨基采酚（5－Br－PADAP）为显色剂，研究了Zn、Mn、Cd──5－Br－PADAP－TritonX－100析相显色体系，建立了同时测定微量锌锰钢的析相光度法。应用于水样中微量锌锰镉的测定，结果满意。2实验部分2．1主要试剂和仪器锌锰镉标准溶液：2mg／L工作溶液，5-Br－PADAP溶液：0．05％乙醇溶液；H3BO3NaOH缓冲溶液pH9．0．TritonX－100溶液：20％水溶液；UV－260型紫外可见分光光度计；pHS－2型酸度计，…     

微柱高效液相色谱法测定环境样品中的铁、钴、镍、铜、锌、锰

研究了用 2-(2-喹啉偶氮 )-间苯二酚 (QAR)为柱前衍生试剂 ,以WatersXterraTM RP18(1 .0×5 0mm ,2. 5 μm)微柱为固定相 ,60 %的甲醇 (内含 0 . 5 %的醋酸 )为流动相 ,高效液相色谱分离、二极管矩阵检测器测定铁、钴、镍、铜、锌和锰的方法。根据信噪比 (S N =3 )得各金属离子的检测限分别为 :铁3 μg L、钴 4μg L、镍 2 μg L、铜 4μg L、锌 5 μg L、锰 8μg L ,方法用于环境样品中痕量铁、钴、镍、铜、锌、锰的测定 ,相对标准偏差在 1 . 6%～ 3 . 5 %之间 ,标准回收率为 93 %～ 1 0 7%。     

速差动力学分光光度法同时测定镍和锌

研究了镍与 5 Br PAN S显色反应的动力学特性。在pH 6.0条件下 ,当[5 Br PAN S]:[Ni2 + ]≥ 2 1 .6时 ,该反应在常温下数分钟内即能完成 ,并测得其表观摩尔吸光系数为 5 .0 0× 1 0 4 L·mol-1·cm-1,求得表观活化能为 44 34kJ mol。利用 5 Br PAN S与镍反应速率较慢 ,建立了一种准确测定混合体系中镍和锌含量的速差动力学分光光度法。方法已应用于电镀废液中镍和锌的同时测定。     

混合线性分析-分光光度法同时测定微量锌、镉、汞

提出了以2－（5－溴－2－吡啶偶氮）－5－二乙氨基酚为显色剂分光光度法同时测定锌、镉、汞的新方法。由于在可见区3种络合物的吸收光谱具有相似的特征和严重重叠,本文采用混合线性分析进行光谱分辨,各组分的纯光谱则用最小二乘法从校正集中求出。讨论了显色条件,波长选择,纯光谱的确定和吸光度加合性等因素对测定的影响。方法具有简单,快速,准确等优点。已成功地应用于混合试样中锌、镉、汞的同时测定,并与同条件下偏最小二乘法的计算结果进行了对比。     

电感耦合等离子体原子发射光谱(ICP-AES)法和电感耦合等离子体质谱(ICP-MS)法测定大气降尘中的铅、镉、铬、锌、锰、镍、铜、铊

大气中Pb、Cd、Cr、Mn、Ni、Tl等重金属污染物是目前国内外城市大气污染的主要因子之一,研究大气降尘中重金属元素含量具有重大意义。本文采用盐酸-硝酸混合酸为消解体系,在105℃条件下用电热板消解回流大气降尘样品2小时后定容测定,通过电感耦合等离子发射光谱法仪(ICP-AES)和电感耦合等离子体质谱仪(ICP-MS)测定大气降尘中铅、镉、铬、锌、锰、镍、铜和铊等8种重金属元素。测定结果表明： ICP-AES(铅、镉、铬、锌、锰、镍、铜)和ICP-MS(铊)两种方法的曲线线性好,准确度高,测定范围宽,检出限在0.024mg/kg-0.548mg/kg之间,精密度在0.15%-2.38%之间,能准确测定大气降尘中的重金属元素含量。     

火焰原子吸收光谱法测定土壤中金属元素

土壤样品用硝酸-氢氟酸-高氯酸(5+5+3)混合酸消解后,采用火焰原子吸收光谱法分别测定了试样溶液中铁、锰、铜、锌、铅、镉和镍的含量。因消解过程中加入了氢氟酸,大部分硅生成四氟化硅气体除去,可在此溶液中直接测定其中铁、锰、铜、锌及镍的量。考虑到SiO_3~(2-)、Ti(Ⅳ)及Al~(3+)对锰测定有负干扰,加入一定量的氯化钙溶液作为释放剂消除其干扰。如试样含铁量较高,须加入硝酸镧溶液作释放剂以克服其对锌测定的干扰。测定铅及镉时须加入碘化钾溶液使之生成碘化物络阴离子后,用4-甲基-2-戊酮作溶剂进行萃取分离,随后在有机相中测定铅与镉的含量。用7种元素的标准溶液制作了各自的标准曲线,所得线性回归方程的相关系数在0.999 2～0.9996之间。以土壤样品为基体,加入一定量7种元素的标准溶液做回收试验,得到回收率在96.8%～99.9%之间,相对标准偏差(n=6)在0.9%～2.0%之间。     

2—（5—溴—2吡啶偶氮）—5—二乙氨基酚与Yb（Ⅲ）络合平衡的双系列线性回归法研究

用双系列线性回归法研究了Yb(Ⅲ )与 5 Br PADAP的络合反应 ,发现在 pH 9.6 6 ,30 %(体积分数 )的乙醇溶液中 ,Yb(Ⅲ )与 5 Br PADAP形成 1∶2的络合物 ,络合物的稳定常数 (lgβ)为 7.58,最大吸收波长为 580nm ,摩尔吸光系数为 2 .0 9× 10 5L·mol- 1·cm- 1     

电感耦合等离子体原子发射光谱法同时测定锌冶炼酸浸渣中12种元素

建立电感耦合等离子体原子发射光谱(ICP–AES)同时测定锌冶炼酸浸渣中铅、铜、铁、镉、钴、镍、锑、钙、镁、铝、砷、锰12种元素的方法。样品采用硝酸–盐酸–氢氟酸–高氯酸四酸溶解,以体积分数为10%的盐酸–硝酸混合溶液为介质,在优化的实验条件下,用电感耦合等离子体原子发射光谱法测定各元素含量。铜、铅、铁、镉、钴、镍、锑的质量浓度在0.10～50μg/mL范围内,钙、镁、铝、砷、锰的质量浓度在0.10～10μg/mL范围内与光谱强度呈良好的线性关系,相关系数均大于0.999,方法检出限为0.002 1～0.025 5μg/mL。测定结果的相对标准偏差为0.012%～1.87%(n=6),样品加标回收率为99.0%～100.3%。采用该方法测定锌精矿成分分析标准物质和实验室内控样品,测定值与参考值基本一致,相对误差为0.00～3.33%。该方法简单、快速,具有较高的准确度和精密度,适用于锌冶炼酸浸渣样品中多元素同时测定,在锌冶炼行业具有重要的应用价值。     

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.     

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.     

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%).     

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.     

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.     

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.