电感耦合等离子体原子发射光谱(ICP-AES)法测定铅锌精矿中铊

采用HCl-HNO_3-HF-HClO_4四种酸溶解铅锌精矿样品,稀释后用电感耦合等离子体原子发射光谱(ICP-AES)法测定其中的铊元素,测定范围0.005%~0.05%。实验确定了介质酸浓度、干扰元素的校正方法。方法相对标准偏差(n=7)为1.3%~4.8%,加标回收率为93.7%~102%,方法干扰少、快速、结果准确,适用于大批量铅锌精矿样品中铊的测定。     

电感耦合等离子体原子发射光谱(ICP-AES)法测定再生锌中铊

铊是一种典型的危险废物,在选冶过程中,再生锌原料中的铊以氧化物或粉尘的形式排放到环境中,严重污染环境并危害人类健康。再生锌成分复杂,若样品消解不完全,直接影响测定结果的准确性。本文比较了微波消解和电热板常压消解对样品的处理效果。结果表明,微波消解法快速环保,但是对于难消解的再生锌样品,因无高氯酸的加入,其氧化性能降低,无法将样品消解完全,导致铊测定结果偏低。而采用高氯酸-硝酸-盐酸-氢氟酸构成的混合酸并于低温加盖聚四氟乙烯盖,进行电热板常压消解,能够有效地解决再生锌样品前处理难题。本实验采用四酸法消解样品,5%盐酸进行浸取,选择Tl 190.794nm为分析谱线,采用电感耦合等离子体原子发射光谱（ICP-AES）法测定再生锌中铊。在仪器设定的最佳测定条件下,当Tl质量浓度为0.10μg/mL~5.00μg/mL时,与发射强度线性关系良好,线性回归方程为y = 180.77x -0.46,相关系数为0.99998。干扰实验表明,在设定的共存离子干扰上限,Pb、Zn、Cu、Fe、Ca、Bi 、Sb、Sn、As、Al、Cd、Si、Ag等对再生锌中铊的测定基本无影响。按照实验方法,对5个不同铊含量水平的再生锌样品进行11次独立测定,其测定范围为ω(Tl):0.0041%~0.21%,方法检出限为0.004μg/mL,实验相对准偏差（RSD）为2.07%~3.11%,加标回收率为97.3%~107.5%。方法简单,操作性强,能够快速准确测定再生锌中铊。     

测定痕量铊的泡沫塑料吸附分离-镉试剂2B分光光度法

研究了在 pH11.5～12.5的NH3 -NH4Cl介质和TritonX -100存在下 ,镉试剂2B与铊 (Ⅲ )的显色反应。铊 (Ⅲ )与镉试剂2B形成摩尔比为1∶4的红色配合物 ,在测定波长500nm处 ,表观摩尔吸光系数为9.3×104 L·mol-1·cm-1 。室温下显色反应瞬间完成 ,配合物至少稳定12h ,线性范围是0～800μg/L。建立了采用聚胺酯泡沫塑料吸附铊 (Ⅲ ) ,与其他干扰元素分离 ,在水相体系快速、准确测定地质样品中痕量铊的方法。该法回收率为97.0 %～106 % ,5次测定的相对标准偏差不大于4.1 % ,其结果与原子吸收测定值吻合     

电感耦合等离子体质谱法测定土壤中痕量铊的方法研究

采用电感耦合等离子质谱法(ICP-MS)测定土壤中的痕量铊,并对前处理方法进行研究,建立了一种使用HNO_3-H_2O_2-HF酸消解体系测量土壤中痕量铊的方法。该方法在0.00~5.00μg/L范围内线性良好,相关系数为0.999 8,方法检出限为0.1 ng/kg,对4份铊土壤标准样品测定的结果均在保证值范围内,RSD为1.8%~6.6%,2份土壤实际样品的加标回收率为95.4%~102.4%。     

光化学催化动力学法测定痕量铊

基于在紫外光的照射下铊对光泽精-过氧化氢体系的光化学催化作用,提出了光化学催化动力学测定痕量铊的方法。系统地考察光源、光照时间、试剂用量及共存离子等因素对测定结果的影响,并探讨了该体系光化学催化作用可能的机理,确定了最佳的测定条件。铊(Ⅰ)的线性范围为0.05～0.3mg·mL-1,检出限(3s/k)为0.0081mg·mL-1。该法用于硫铁矿样品中痕量铊的测定,其相对标准偏差(n=6)为3.27%,回收率在80.0%～120.0%之间。     

挥发排锑-电感耦合等离子体质谱法测定铅锑精矿中铊

采用盐硝混酸+氢氟酸溶解样品,氢溴酸挥发除锑的方法,避免高含量锑在溶液中不稳定及对铊测定的干扰,采用电感耦合等离子体质谱法测定了铅锑精矿中铊的含量。铅锑精矿经过前处理后,样品溶液中锑的残留量均小于10μg/m L。选择铱作内标,将方法应用于实际样品中铊的测定,相对标准偏差小于5%,回收率为97.2%~107%,选择6家试验室协同验证,经统计检验测试结果间无明显差异。方法适用于铅锑精矿中铊的测定。     

聚酰胺分离富集置换催化光度法测定痕量铊

研究了在 0 .15～ 0 .0 8mol/L的硫酸介质中 ,用铊 置换出Cu EDTA中的Cu ;Cu 催化溴酸钾氧化偶氮氯瞵 mA褪色的指示反应及其动力学条件 ,据此建立测定痕量铊 的新方法。在 5 5 0nm处 ,检出限为 1.32× 10 -9g/L ;测定范围为 0～ 6 0 0 μg/L ,用聚酰胺在盐酸或王水介质中分离富集样品中的铊 ,使方法的选择性大大提高。用于水及岩石样品中铊的测定 ,相对标准偏差小于 3.7% ;标准加入回收率 96 %～10 4 % ,获得满意结果。     

不同基体改进剂对石墨炉原子吸收法测定土壤和沉积物中铊的影响

应用Pd(NO3)2-抗坏血酸(Vc)基体改进剂,建立了石墨炉原子吸收法(GFAA法)测定土壤和沉积物样品中铊。针对土壤和沉积物复杂基体,GFAA法测定铊元素主要受到氯离子的干扰,文中研究了常见基体改进剂(包括NH4NO3,(NH4)2SO4,La(NO3)3,Mg(NO3)2,Vc,Pd(NO3)2,Pd(NO3)2-Vc)对氯离子的抑制效果。通过研究不同基体改进剂测定含氯铊标准溶液的吸收曲线,探讨出基体改进剂测定铊的作用机理。以土壤或沉积物标准物质为研究对象,优化了应用Pd(NO3)2-Vc测定铊的灰化温度、基改剂浓度以及原子化温度。在最佳实验条件下,通过比较有无基体改进剂条件下,采用GFAA法测定不同土壤和沉积物中铊的精密度和准确度,实验结果表明,应用Pd(NO3)2-VC基体改进剂,测定土壤和沉积物标准物质中铊的测定结果都在标准值范围之内,6次平行测定的相对标准偏差范围为2.8%~8.4%,用于测定实际土壤和沉积物样品加标回收率为128.0%和92.9%。     

离子交换分离-石墨炉原子吸收光谱法测定饮用水中痕量铊

水样经硝酸酸化、蒸发浓缩后,调pH至1.7~2.0;用溴水氧化铊(Ⅰ)为铊(Ⅲ);用D401离子交换树脂分离出铊,而后用石墨炉原子吸收光谱法测定。在pH 1.8附近,铊(Ⅲ)可与砷(Ⅴ)、硼(Ⅲ)、钡(Ⅱ)、铍(Ⅱ)、钙(Ⅱ)、镓(Ⅲ)、钾(Ⅰ)、锂(Ⅰ)、镁(Ⅱ)、锰(Ⅱ)、钠(Ⅰ)、锑(Ⅴ)、硅(Ⅳ)、锶(Ⅱ)、铋(Ⅲ)、铜(Ⅱ)、钛(Ⅳ)和钒(Ⅴ)分离;而铝(Ⅲ)、镉(Ⅱ)、铬(Ⅲ)、铁(Ⅲ)、镍(Ⅱ)、铅(Ⅱ)和锌(Ⅱ)不能与铊完全分离,但一般水样经分离程序后残留下来的这些物质不足以影响对铊的测定。方法的线性范围为25~500pg;测定下限为0.5ng·L~(-1)。方法用于实际样品分析,测定结果与已知值相符,加标回收率在94.0%~110%之间,测定值的相对标准偏差(n=8)在1.9%~15%之间。     

平台原子吸收法测定环境和生物样品中的痕量铊

铊及其化合物有剧毒。它的硫酸盐和乙酸盐已作为杀虫剂和灭鼠剂。铊在环境样品中,如土、气、水和植物等,含量很低,但在冶炼厂的回降物中,烧煤的烟道灰和水泥工业的尘埃中均发现有铊。铊可能造成污染及危害人体健康等情况,不容忽视。然而目前缺少灵敏、可靠的监测痕量铊的方法。石墨炉原子吸收法具有灵敏、取样少和操作简便等优点,目前已广泛应用于环境样品和各种材料中痕量元素的测定。但迄今为止,文献中用于测定铊的报导却很少。Welcher首先用石墨炉测定合金中的铊,指出盐酸对铊产生严重的     

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.     

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.     

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.     

Catalyst free,visible-light promoted photoaddition reactions between C60 and N-trimethylsilylmethyl-substituted tertiary amines for synthesis of aminomethyl-1,2-dihydrofullerenes

An efficient and benign method for the preparation of aminomethyl-substituted fullerenes has been developed. The process, involving catalyst free, visible-light irradiation of 10% EtOH-toluene solutions containing fullerene C₆₀ and N-trimethylsilylmethyl-substituted amines by using a 20 W compact fluorescent lamp, leads to formation of aminomethyl-substituted fullerene adducts in a highly efficient manner. The photoaddition reaction takes place via a pathway initiated by visible light absorption by C₆₀, followed by SET from the amine to the triplet excited state of C₆₀. Ethanol-promoted desilylation of the resulting a minimum radical then generates the corresponding α-amino radical which couples with the C₆₀ radical anion to form the anion precursor of the fullerene adducts. The new approach using visible-light takes place under mild conditions and it does not require the use of photocatalysts. Thus, the method developed in this effort could broadens the range of functionalized fullerene derivatives that can be readily prepared.     

Highly efficient and stereoselective cycloaddition of nitrones to indolyl- and pyrrolylacrylates

The reactions of various nitrones with indolyl- and pyrrolylacrylates proceeds regioselectively with high diastereoselectivity in the case of aldonitrones, and represents an effective method for obtaining new indolyl- and pyrrolyl-substituted isoxazolidine carboxylates stabilized by weak (CH?O) and moderate (NH?N) strength intramolecular hydrogen bonding. The resulting cycloadducts exhibit promising in vitro anti-influenza activities.     

Transition metal-free direct amination of benzoxazoles using formamides as nitrogen sources

A transition metal-free method for the direct amination of benzoxazoles using formamides as nitrogen sources is reported, which was mediated by an inexpensive and environmentally friendly tetrabutylammonium iodide/tert-butyl hydroperoxide system and gave the 2-aminobenzoxazole derivatives with moderate to good yields.     

l-Proline-catalyzed five-component domino reaction leading to multifunctionalized 1,2,3,4-tetrahydropyridines

Multifunctionalized 1,2,3,4-tetrahydropyridines are concisely synthesized in good yields via l-proline-catalyzed or l-proline/FeCl₃-cocatalyzed one-pot multicomponent reactions (MCRs). The MCRs involve a domino hydroamination/prins reaction/Mannich-type reaction/intramolecular dehydration-cyclization process. The molecular structure of 5baa, one of multifunctionalized 1,2,3,4-tetrahydropyridines, was confirmed by single-crystal X-ray diffraction.     

Exploring the scope of the Gewald reaction: Expansion to a four-component process

An efficient four-component reaction was developed to take advantage of the reactivity of the 2-aminothiophene-3-carbonitrile functionality, which is obtained during the classical three-component Gewald reaction. Various α-methylene bearing ketones were reacted with malononitrile, elemental sulfur, and aryl/heteroarylnitrile derivatives in t-BuOH/NaOH to afford 2-arylthieno[2,3-d]pyrimidin-4-amines in high yields. Preliminary studies revealed the photophysical properties of the products and their potential for use as metal sensors.