氢化物负压发生和真空无火焰原子化器的原子吸收光谱法测定铋

在负压发生器中用1% NaBH_4将Bi(Ⅲ)还原为铋化氢后,向发生器中加入一定量的空气。用真空泵将铋化氢和空气的混合物同时吸入到真空电热石英管中,用原子吸收仪器测定。在原子化器内,加入空气中的氧与硼氢化钠分解产生的氢反应,生成水分子。因而消除了氢对测定铋的干扰。     

氢化物负压发生,夹带氧气的真空无火焰原子吸收测量技术测定砷、锑、硒和锡

在负压氢化物发生器中用1％NaBH_4将砷、锑、硒和锡还原成氢化物后,加入一定量氧气,用真空泵将氧与氢化物的混合物吸入到电热石英管中,同时用原子吸收仪器测定。加入的氧与来自硼氢化钠分解产生的氢反应,生成气态水分子,因而消除了氢对测量元素的干扰。     

氢化物原子荧光法测定化探试样中锑和铋

氢化物原子荧光法是近几年来发展起来的一种新的痕量分析方法。该法操作简便,灵敏度高,能满足测定化探样品中痕量锑和铋的要求。本法采用锑、铋无极放电灯作为激发光源,将试样溶液加入氢化物发生器的反应瓶中,以硼氢化钾作还原剂,生成锑化氢及铋化氢气体,在氩-氢火焰中受热分解和原子化,它们吸收由无极放电灯辐射出来的特征谱线后,发出荧光信号。由于原子荧光谱线的荧光强度与试液中锑、铋的含量成线性关系,所以根据测定的荧光信号值即可求出化探样品中锑及铋的     

硒、碲氢化物发生的反应机理和反应条件

元素周期表中ⅣA,ⅤA及ⅥA族元素的化学及物理性质的周期性变化引起硒、碲两元素的氢化物生成反应机理的改变。文中对两元素生成氢化物的反应机理作了解释,认为是硒(Ⅳ)[或碲(Ⅳ)]在盐酸溶液中与初生态氢[H]反应的结果。初生态氢是由硼氢根(BH4-)在酸溶液中水解而产生,反应时随氢离子(即酸度)浓度的增加,氢化物的生成率将明显提高。此外,不断地将氢化物发生反应中同时生成的水蒸气除去不仅可避免硒(碲)氢化物被氧化,而且还可提高其产出率和峰值测定的重现性。对如何规范使用低熔点、高强度空心双阴极灯也作了评价。     

水对甲醇在电解银上氧化反应的影响

本文运用超高真空程序升温反应谱(TPRS),结合瞬变应答和同位素交换方法研究了电解银上氧致甲醇吸附和反应的机理以及水对甲醇氧化的影响.实验结果表明:吸附态的氧能显著增加甲醇的吸附并和甲醇反应生成水;水中的氧来源于吸附态氧,氢来源于甲醇中的甲基氢和羟基氢且以甲基氢居多.水和氧在电解银表面上存在着竞争吸附,水的加入能抑制甲醇氧化为甲醛的副产物CO_2的产生,提高反应选择性.此结果与活性数据一致.     

金盘电极用于硒和碲的伏安法研究及其环境样品中硒和碲的测定

本文对固体电极特别是金电极的性能和在水溶液中的氧吸附行为以及伏安特性做了一些文献调研和实验,针对毒性元素硒和碲,研究了它们在固体电极上的沉积-溶出过程,并将金电极用于硒和碲的分析测定,为环境科学中硒和碲的监测提供了一个有用的方法。     

二氢茉莉酮酸甲酯的合成研究

二氢茉莉酮酸甲酯是非常重要的人工合成香料,其合成方法是有机合成工作者研究的重点。以2-戊基-2-环戊烯-1-酮为原料,经Michael加成/脱甲氧羰基合成二氢茉莉酮酸甲酯是常用的合成路线。本文着重对脱甲氧羰基步骤进行了优化。尝试加入卤盐以降低该反应温度,发现盐的加入导致逆Michael加成产物的生成,致使产率较低。又研究了将Michael加成产物单水解然后脱羧的方法,该方法不仅降低了反应温度,而且使用更易处理的DMF为反应溶剂,经两步反应以85%的产率得到二氢茉莉酮酸甲酯。     

电热石墨炉原子吸收法测定矿样中微量硒、碲

硒、碲是金属中有害元素,虽含量极微,但直接影响产品质量。分析中通常采用比色法和极谱法。对高纯铜、高纯镍中硒、碲的电热石墨管炉法测量已有报导。其步骤是将样品硝酸溶解后稀释至一定体积,与纯标准中加入大量基体的测定进行比较。Michael、Bed     

Pt/TiO_2催化剂上的氢—氧作用——Ⅱ. 程序升温还原和程序升温氧化研究

本文采用TPR、TPO技术分别考察了氧处理Pt/TiO_2上氧物种的还原行为和氢还原样品的氧化过程.TPR结果表明,表面含有活泼氧物种的Pt/TiO_2样品对氢很活泼,室温条件下可以吸附大量氢,并且这些吸附氢又可以在TPR过程中脱附.表面活泼氧物种与氢的反应温度在500—673K之间,当大于673K时,Pt/TiO_2继续耗氢,可能是氢与还原产生的表面Ti~(3+)离子进一步反应生成钛—氢物种,并向TiO_2体相扩散与TiO_2体相晶格氧发生反应.对于773K还原的Pt/TiO_2作品,室温吸附氧在TPD过程中可以与表面吸附氢反应;473K氧化处理可以消除表面的吸附氢,但并不能完全去除体相储氢;573K氧化处理则基本上恢复了原样品的氧化状态.不同温度氢还原处理的Pt/TiO_2样品在动态氧化过程(TPO)中,在300-600K温区,气相氧与样品上表面吸附氢和表面氧空位反应;在大于600K温区,氧主要与表面钛—氢物种发生反应,并向体相扩散,与体相氢发生反应.文中描述了气相氢、氧分别与Pt/TiO_2催化剂存在的氧或氢物种作用的形式.     

Ni-Fe/Ti和Ni-Fe-S/Ti的制备及其电催化水分解性能

以钛网为基底,采用电沉积法制备了Ni-Fe/Ti析氧电极,然后将得到的Ni-Fe/Ti电极通过固相硫化制备了Ni-Fe-S/Ti析氢电极. 分别考察了电沉积液中Ni ²⁺/Fe ³⁺离子摩尔浓度比和硫脲加入量对Ni-Fe/Ti和Ni-Fe-S/Ti结构和电化学性能的影响. 结果表明,随着电沉积液中Ni ²⁺含量的增加,Ni-Fe/Ti电极析氧性能先增强后减弱,Ni9Fe1/Ti电极具有最好的析氧性能;随着硫脲加入量的增加,Ni-Fe-S/Ti电极析氢性能呈现先增强后减弱的趋势,Ni9Fe1S0.25/Ti电极具有最好的析氢性能. 在50 mA·cm ^-2下,Ni9Fe1/Ti电极的析氧过电位为280 mV,Ni9Fe1S0.25/Ti电极的析氢过电位为269 mV,且均具有很好的稳定性. 将Ni9Fe1/Ti与Ni9Fe1S0.25/Ti分别作为阳极和阴极进行电催化全水分解,电流密度达到50 mA·cm ^-2所需电势仅1.69 V,表现出很好的全水解催化性能.     

Determination of antimony, arsenic, bismuth, selenium, tellurium and tin by low pressure atomic absorption spectrometry with a quartz tube furnace atomizer and hydride generation with air addition

A new method has been developed for the determination of antimony, arsenic, bismuth, selenium, tellurium and tin by hydride generation-atomic absorption spectrometry in an electrically heated quartz tube furnace under sub-atmospheric pressure. The hydride generator, operating at a pressure lower than atmospheric, is used to generate and collect the hydrides of these elements. A certain volume (at atmospheric pressure) of air is then added to the generator after the formation of the volatile hydride. The gaseous mixture of the hydride and air is drawn into an evacuated, heated quartz tube by a vacuum pump. The proposed method gives improved sensitivities and detection limits.     

Determination of Tellurium by Gas Phase Molecular Absorption Spectrometry After Hydrogen Telluride Generation

Abstract

A method for determination of tellurium(IV) or tellurium(VI) is described that involves hydrogen telluride generation by reduction with sodium tetrahydro-borate(III), evolution of hydride with HCl solution, transport into a flow-cell placed in a UV-visible molecular absorption spectrophotometer and measurement of gas at 190 nm. Hydride generation and determination procedures are optimized, based on height and area of absorbance versus time profile of hydrogen telluride generated. Using the best experimental conditions found the calibration curve is linear from 5 to 100 μg/ml of tellurium, 1.1 μg/ml of tellurium(IV) or 3.1 μg/ml of tellurium(VI) can be detected, and relative standard deviation ranges from 4 to 7%. The method is applied to the analysis of additives for synthetic rubber making.     

氢化物发生-原子荧光光谱法(HG-AFS)测定特硬铅合金中硒和碲

建立了氢化物发生-原子荧光光谱法(HG-AFS)测定特硬铅合金中硒和碲的分析方法。试样经硝酸和酒石酸溶解,硫酸沉淀分离基体铅元素。移取部分试液,在40%盐酸介质中直接用氢化物发生-原子荧光光谱法(HG-AFS)测定样品中的硒;另移取部分试液,加入氢溴酸挥发除去砷、锑、锡、硒等元素,在40%盐酸介质中用氢化物发生-原子荧光光谱法(HG-AFS)测定样品中的碲。考察了测定的最佳条件、铅及共存元素对测定的影响。测定硒和碲的相对标准偏差分别为7.5%～9.3%和3.6%～13.0%,加标回收率分别为88%～92%和98%～102%。准确度和精密度均能满足分析需要,具有较强的实用性。     

Atomic absorption spectrometric determination of trace tellurium after hydride trapping on platinum-coated tungsten coil

In this work, a sensitive and simple method for the determination of tellurium was developed by hyphenation of electrically heated quartz tube atomic absorption spectrometry and tellurium hydride trapping on platinum-coated tungsten coil. With a mixture of Ar and H₂, tellurium hydride was transported to tungsten coil for trapping at 390 °C and releasing at 1200 °C. A limit of detection (LOD, 3σ) of 0.08 ng mL^{− 1} was obtained with 1 min trapping (1.5 mL sampling volume), and enhancement factor was 28 compared to conventional hydride generation atomic absorption spectrometry. The LOD was better or at least comparable to literature levels involving on-line trapping and some other sophisticated instrumental method such as graphite furnace atomic absorption spectrometry (GF-AAS) and inductively coupled plasma mass spectrometry (ICP-MS), and it can be further lowered down to 0.03 ng mL^{− 1} by increasing the trapping time to 4 min. The platinum coating was stable for 300 firings without sensitivity loss. Interference and its alleviation were studied in detail. The proposed method was applied to the determination of tellurium in several geological standard reference materials, and the results were found in good agreement with the certified values.     

Investigation of thallium hydride generation using in situ trapping in graphite tube by atomic absorption spectrometry

Thallium hydride was generated from aqueous solutions by merging sample and sodium tetrahydroborate reductant in a batch system. In situ preconcentration of volatile thallium hydride in a preheated graphite furnace coated with palladium, which was used as both the collection medium and atomizer, greatly improved the sensitivity for the determination of thallium by hydride generation atomic absorption spectrometry. The presence of tellurium can increase the generation efficiency of thallium hydride. The operating conditions were optimized. The calibration graph is linear up to 100 ng and the characteristic mass for thallium was 0.92 ng which is seventeen times lower than that obtained with the heated quartz tube atomizer.     

Simultaneous determination of bismuth and tellurium in steels by high power nitrogen microwave induced plasma atomic emission spectrometry coupled with the hydride generation technique

An annular-shaped, high power nitrogen microwave induced plasma (N₂-MIP) produced at atmospheric pressure by an Okamoto cavity, as a new excitation source for atomic emission spectrometry (AES), has been used for the simultaneous determination of bismuth and tellurium in steels with the hydride generation method. Under the optimized experimental conditions, the best attainable detection limits at the Bi I 195.389 nm and Te I 200.200 nm lines were 110 and 86 ng/ml for bismuth and tellurium, respectively. The linear dynamic ranges for bismuth and tellurium were 300 to 30,000 ng/ml. The presence of several diverse elements was found to cause a more or less depressing interference with the proposed technique. When bismuth and tellurium in steels were determined, a large amount of Fe(III) in the solution caused a severe depressing interference, while the presence of Fe(II) showed little or no significant interference. Of the several interference-releasing agents examined, l-ascorbic acid was found to be the most preferable to reduce Fe(III) to Fe(II) prior to hydride generation. The concentrations of bismuth and tellurium in steels were determined by the proposed technique. The results obtained by this method were in good agreement with their certified values.     

Determination of the hydride concentration in alkyldiboranes(6) by 11B NMR spectroscopy – Reduction of inorganic selenium and tellurium compounds

As an alternative to volumetric analysis, ¹¹B NMR spectroscopy can be used to determine the hydride concentration and the relative amount of different active hydride species in mixtures of alkyldiboranes(6) (alkyl = Et, Pr). Inorganic selenium(IV) compounds react with propyldiboranes(6) at first to give elemental selenium (hydride number HN = 4) and after prolonged heating at 130?°C to selenides (HN = 6). In contrast, tellurium(IV) and tellurium(VI) compounds are reduced only to elemental tellurium.     

Determination of the hydride concentration in alkyldiboranes(6) by 11B NMR spectroscopy – Reduction of inorganic selenium and tellurium compounds

As an alternative to volumetric analysis, ¹¹B NMR spectroscopy can be used to determine the hydride concentration and the relative amount of different active hydride species in mixtures of alkyldiboranes(6) (alkyl = Et, Pr). Inorganic selenium(IV) compounds react with propyldiboranes(6) at first to give elemental selenium (hydride number HN = 4) and after prolonged heating at 130 °C to selenides (HN = 6). In contrast, tellurium(IV) and tellurium(VI) compounds are reduced only to elemental tellurium. Received: 31 March 1998 / Accepted: 26 April 1998     

The determination of tellurium by nondispersive atomic fluorescence spectrometry using the hydride generation technique

Atomic fluorescence spectrometry with a nondispersive measuring system is combined with a hydride generation technique for the determination of tellurium. Atomic fluorescence measurement is based on the reduction of tellurium by either metallic zinc or sodium borohydride, introduction of the generated tellurium hydride into a premixed argon (entrained air)-hydrogen flame, and excitation with a tellurium electrodeless discharge lamp. The comparison of the zinc and the sodium borohydride reduction methods is discussed in terms of detection limit, precision and interference. The best attainable detection limits for tellurium are 2ng (0.1 $\text{ng}\text{ml}$) and 30 ng (1.5 $\text{ng}\text{ml}$) with the zinc and the sodium borohydride methods respectively. Analytical working curves obtained from peak-height and peak-area measurements are linear over a range of approximately 4 orders of magnitude. Of the mineral acids examined in the range up to 2.0 m. nitric acid gives a depressing interference in the range greater than 0.5 m in the zinc method, whereas all of the acids greater than 1.0 m give a slight enhancement of the signal in the sodium borohydride method. The presence of several elements including other hydride-forming elements in 1000-fold ratio to tellurium causes a depressing interference, while enhancing interferences from tungsten and vanadium are observed in the zinc and the sodium borohydride methods, respectively. The present system coupled with the zinc method has been applied to the determination of tellurium in several samples of high-purity copper metal after separation of the analyte from copper by passing an ammoniacal solution of the sample through Chelex-100 resin. The results are in good agreement with those obtained by graphite furnace atomic absorption spectrometry.     

Ion chromatography–hydride generation‐atomic fluorescence spectrometry speciation of tellurium

The speciation of tellurium was carried out using atomic fluorescence spectrometry as an element‐specific detector in hybridization with liquid chromatography and hydride generation. Good resolution could be obtained by anion‐exchange chromatography with complexing agents, using a mobile phase with 8 mM EDTA and 2 mM potassium hydrogenphthalate. Analysis time was less than 6 min. Calibration graphs were linear between 2 and 100 µg l^?1. Detection limits were 0.6 µg l^?1 and 0.7 µg l^?1 for tellurium(VI) and tellurium(IV) respectively. The method was applied to the speciation of tellurium in drinking water and wastewater samples from different metallurgical industries. Copyright © 2005 John Wiley & Sons, Ltd.