火焰原子吸收光谱法测定合金钢中高含量镍

钢中加入适量的镍能使钢具有优良的机械性能、耐热性、抗腐蚀性、可焊性和高导磁性等。因此镍的分析在合金钢中十分重要。目前测定合金钢中高含量镍的方法主要为丁二酮肟分离-EDTA滴定法、丁二酮肟重量法和碘氧化-丁二酮肟光度法,存在分析流程冗长,消耗试剂量多,精密度低的不足。国家标准方法GB 223.54-1987采用火焰原     

ICP-AES法检测工业用精对苯二甲酸中金属元素

研究用ICP-AES法同时测定工业用精对苯二甲酸中铬、钴、铁、锰、钼、镍、钛等金属元素.通过实验确定了入射功率、冷却气流量、辅助气流量、雾化压力等实验条件.该方法的检出限为0.0013～0.0148 mg/L,测定结果的相对标准偏差为0.16%～0.30%(n=11),加标回收率为90.6%～96.2%.该方法对试样的测定结果与原子吸收分光光度法及二安替比林甲烷分光光度法的检测结果基本一致.     

柠檬酸-罗丹明B体系阻抑动力学光度法测定痕量钴(Ⅱ)

催化动力学光度法以其灵敏高、检出限低,受到人们广泛重视.催化动力学光度法常用分析方法［1］有催化氧化动力学光度法、催化还原动力学光度法、催化荧光光度法、阻抑动力学光度法等.催化动力学光度法其检测限都在 ng·mL-1级,通常用于痕量分析,尤其适用于痕量金属离子测定.催化氧化动力学光度法测定痕量钴已有报道［2-5］,而阻抑动力学光度法测定痕量钴报道较少［6,7］.本文研究发现,在NH3·H2O-NH4Cl （pH=9.5）缓冲介质中柠檬酸对双氧水氧化罗丹明B的褪色反应具有阻抑作用,加入钴(Ⅱ)离子后,阻抑作用明显加强,且阻抑作用与加入的钴（Ⅱ）离子浓度成正比.据此建立了利用钴(Ⅱ)-柠檬酸对双氧水氧化罗丹明B褪色反应的催化阻抑动力学光度法来测量痕量钴的方法.该方法用于VB12药品针剂中痕量钴的测定获得较为满意的结果.     

差示光度法测定铜电解液中高含量铜

在粗铜电解精炼过程中,铜电解液中铜的测定常用碘量法,由于As(Ⅱ)等杂质的干扰,须经过掩蔽和氧化等预处理,操作时间较长,且结果稳定性较差.差示光度法具有测定高含量的优点,本文利用在硫酸介质中铜离子的本色,寻求差示光度法测定铜的各种条件,拟定了铜电解液中铜的快速测定法.本法操作简便,稳定性好,结果与碘量法相吻合.     

K系数分光光度法同时测定钴矿中铜、钴、镍

探讨了在pH 8.00时,溴化十六烷基三甲基铵在存下,铜(Ⅱ)、钴(Ⅱ)和镍(Ⅱ)与二甲酚橙显色的反应条件.建立了K系数分光光度法同时测定钴矿中铜、钴、镍的分析方法.铜、钴、镍含量分别在0～800 μg·L-1,0～1.60 mg·L-1,0～1.20 mg·L-1范围内符合比耳定律.方法用于钴矿试样的分析,测得铜、钴、镍的相对标准偏差分别为3.5%,4.9%,3.4%,回收率分别为103.3%,92.6%,99.0%.     

分光光度法测定合金钢中的钼

建立了采用氯化亚锡还原-分光光度法测定合金钢中钼的方法,研究了实验条件对检测结果的影响,用测定已知钼含量的合金钢标准样品,选定最佳检测条件,在选定的实验条件下对样品中钼含量进行检测,其结果与传统的测钼方法得到的结果吻合,方法省时省试剂,能快速准确测得合金钢中的钼。     

电位滴定法测定弹性合金中的高含量钴

采用电位滴定法测定弹性合金中的钴元素。探讨了弹性合金中基体元素铁,主量元素如铬、锰、钼、镍、钨等对钴元素测定的干扰情况,确定了合适的样品处理方法,同时进行了铁氰化钾用量及滴定溶液温度控制等条件试验。测定结果的相对标准偏差为0．19％-0．28％（n=8）,回收率为99．9％-100．8％。该方法可以满足弹性合金中高含量钴元素的测定要求。     

金属材料分析方法的选择和施行第三讲钢铁中钼的测定(续)

2 .8　其他测定钼的光度分析法从以上所述可见硫氰酸盐光度法测定钢铁或合金中钼的方法在选择性、灵敏度及准确性等方面并非十分理想。在众多的分析化学文献中 ,可以找到很多钼的光度测定方法。但都各自存在一定的缺点而未能完全适合钢铁分析的要求。现从中选择三则有一定实用意义和应用前景的方法供参考和选择。(1)方法 1　 2 氨基苯硫酚萃取光度法测定合金钢中钼 (摘自ＣｈａｒｋｒａｂａｒｔｉＡ .Ｋ .ｅｔａｌ.Ｔａｌａｎｔａ1976 ,2 3:736 )适用范围 :可用于含铬、钨、钒的合金钢测定范围 :ｗ(Ｍｏ) 0 .1%～ 6 .0 %方法提要 :(ａ)溶样…     

三元配合物薄层树脂相光度法测定天然水中痕量钴的研究

在酸性条件下(pH 5), 利用阳离子交换树脂-丁二酮肟-碘-钴四元体系, 在454 nm处具有最大吸收, 确定了借助薄层树脂相光度法测定钴的新方法.本法灵敏度高(ε454=1.7×105 L·mol-1·cm-1), 比水相光度法提高14倍, 精密度高(测定2.0 μg/mL Co(Ⅱ) 6次, RSD=1.3%), 选择性好. 实测天然水中钴,线性范围0.024～2.0 μg/mL, 检出限10.4 ng/mL.     

金属材料分析方法的选择和施行第三讲钢铁中钼的测定(续)

2 .10　钢铁中钼的重量测定法在本讲 1.1节中已提到有不少种类的合金钢及镍基合金中 ,为了获得耐腐蚀、耐高温及耐磨等多种性能 ,常加入较高含量的钼作为合金元素。从 2 .2节至 2 .8节所引述的方法 ,均不适用于含钼 2 %以上的试样中钼的测定。 2 .2节方法 2系ＪＩＳ标准 ,其测定范围定为 <9% ,可认为对含钼高达 9%的试样也能适用。但笔者认为应用该方法测定高含量钼 ,其准确度和精密度均不能满足实际需要 。正如ＩＳＯ4 94 1标准方法在第一版发布时也将钼的测定范围的上限定为 9% ,但在 1994年发布第二版时已将测定范围的上限修订为 0 .12 …     

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.