石墨炉原子吸收光谱法测定痕量钒的研究

本文采用石记原子吸收光谱对钒吸收线的特征，普通石墨管和热解石墨管中钒的原子化行为，灰化和原子化条件，基体效应等进行了研究，综合应用基体改进剂，光控升温和解石墨管技术，提高了电热原子吸收测定钒的灵敏度，特征质量为２４ｐｇ／０．００４４Ａ。     

氢化物发生石墨炉原子吸收进展

在氢化物发生原子吸收光谱中,石英管是使用较为广泛的原子化器,但由于其气相干扰比较严重,石英管表面性质对分析灵敏度影响较大,因而又发展了石墨炉原子化器。自提出涂钯石墨管原位富集氢化物以后,氢化物发生石墨炉原子吸收受到人们的重视。现将氢化物发生石墨炉原于吸收的主要方法分述如下: 1 石墨炉在线原子化法 所谓石墨炉在线原子化法,是将生成的氢化物直接通入已经达到原子化温度的石墨管里的方法。氢化物可以从石墨炉内气路通入石墨管,也可以从石墨管进样孔进入石墨管。由于石墨炉原子化的温度较高,因而能大大减小可以形成氢化物元素的气相干扰。文献[1]比较了石英管和石墨管两种原子化器的抗干扰能力,其中有关砷和硒的干扰情况见表1。     

镧涂层表面效应初探

本实验通过对涂镧石墨管和非涂镧石墨管的电子显微分析，证实了镧涂层并未能对石墨管壁的孔洞起到有效的填充作用，这与测定金时吸收信号未明显变化的实验现象相吻合。通过对锡原子化前后石墨表面的Ｘ光电子谱分析，尝试提出了镧在管中的催化作用及影响某些元素原子化机理、从而改变其灵敏度的观点。     

石墨管测试性能的研究及在无焰原子吸收法测定化探样品痕量银镉铍中的应用

本文详细研究了各种石墨管的测试性能和实际应用,对各种石墨管的记忆效应,灵敏度检测限,精密度和抗酸能力进行了比较,并研究了各种石墨管对银、镉、铍的灰化和原子化温度及在样品分析中的适应性。发现不同元素应选用不同厂家的石墨管是重要的,拟定了加入基体改进剂后的直接测定程序,应用于地球化学标样中痕量银、镉、铍的测定,其结果与可用值相符。本工作对其它元素测定和石墨管种类选择,也具有普遍的借鉴作用。     

石墨炉原子吸收光谱法的石墨管表面的难熔碳化物涂覆处理

廿余年来,电热石墨炉已发展成为应用较为广泛的一种最有代表性的电热原子化器。关于电热石墨炉原子吸收光谱法的许多研究报告都指出石墨管的表面状态与测定灵敏度、检出限、精密度、记忆效应、管     

涂层平台技术用于石墨炉原子吸收光谱法测定矿石中痕量金

关于改善石墨炉原子吸收光谱分析特性已有不少报导,其中以平台原子化技术和以难熔碳化物形式涂覆于石墨管表面的涂层技术具有成本低、简便易行的特点。本文则以氯氧酰锆涂覆处理平台(即涂层平台技术),不但解决了石墨管性能差异所引起的灵敏度差别,同时提高了灵敏度、稳定性,延长了石墨管使用寿命。本法用于矿石中痕量金的测定,灵敏度(特征浓度)为0.0004微克/毫升(1%吸收),变异系数小于10%。适用于地质样品中0.001～     

衬钽石墨炉原子吸收分光光度法测定水中痕量钡

石墨炉原子吸收分光光度法广泛地应用于痕量分析,但常局限于测定低温和中温元素。相当多的元素与石墨管形成稳定的碳化物,测定灵敏度低,常伴有记忆效应,石墨管也易损坏。钡属于形成碳化物的元素之列,而且特征波长在可见区,石墨管在高温下的背景发射影响测定。为了克服碳化物的影响,通常采用以下解决办法。常用的碳化物涂层法,虽然文献报导较多,但处理过程比较麻烦,而且结果重现性差,对钡的效果并不明显。也有使用热解石墨管测钡的,灵敏度有不同程度的提高。用金属原子化器。测定钡,灵敏度有所提高,但在通常的石墨炉上直接采用有一定的困难。还有在标准石墨管中衬入高熔点的金属     

平台石墨炉原子吸收法测定环境样品中锡

石墨炉原子吸收测定锡的方法具有灵敏度高取样量少的优点,目前已被广泛地应用,但锡易与石墨管表面反应及锡的硫化物和氧化物的易挥发性质,使测定方法存在着原子化效率低,基体干扰严重和测量再现性差等问题。许多作者研究将石墨管表面涂层改性处理,期望提高锡原子化效率及再现性,用基体改进剂硝酸铵,抗坏血酸和磷酸二氢铵消除或降低基体干扰。近几年发展的L＇vov平台技术的应用,对某些元素在提高灵敏度和改善基体干扰方面已获得良好效果。     

涂钨石墨管石墨炉原子吸收光谱法测定人参中锗

石墨炉原子吸收法测定锗的问题主要是样品原子化前会形成易挥发的GeO,影响分析灵敏度。有关测锗的报道见文献。本工作应用CCl_4萃取和水反萃取,涂钨石墨管石墨炉原子吸收测定人参中锗,获得满意的结果。     

钨钽石墨管原子吸收光谱法直接测定土壤中痕量钕和钪

本文采用一种新型石墨管原子化器—钨钽石墨管,测定钕和钪。与普通热解涂层石墨管相比,灵敏度提高五倍多,1％吸收灵敏度钕为3.2×10~(-10)克,钪1.0×10~(-11)克;消除了记忆效应,提高了工作效率;原子化温度降低100多度,管的使用寿命延长1～3倍,达200次以上,测定精密度在5％以内;抗基体元素的干扰能力较好。土壤中20ppm以上的钕和200ppb以上的钪无需预分离富集,可以直接测定,结果与中子活化法一致。该方法简便、准确。     

Glassy carbon tubes for electrothermal atomic absorption spectrometry

Summary The use of glassy carbon as a tube material in electrothermal atomic absorption spectrometry requires modifications to the power supply if temperatures and heating rates comparable to those for graphite tubes are to be obtained. Glassy carbon tubes frequently have a longer lifetime than pyrolytic graphite coated tubes made of polycrystalline electrographite. Peak height sensitivity for glassy carbon is better by a factor of two for some volatile elements, but up to a factor of five inferior for less volatile elements than that for pyrolytic graphite coated tubes. Peak area sensitivity is generally inferior by about a factor of two. Sample volume is limited to 5–10 l because of the smooth surface.From the signal shape it can be deduced that adsorption of analyte atoms at the tube wall plays an important role in glassy carbon, and is responsible at least in part for the lower sensitivity. Non-spectral interferences can be less pronounced in glassy carbon tubes for those interferents which interact with graphite tube surfaces. Glassy carbon is, however, no alternative to pyrolytic graphite coated tubes.

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Glasartiger Kohlenstoff als Rohrmaterial für elektrothermische Atomabsorptionsspektrometrie

     

Transverse heated filter atomizer for electrothermal atomic absorption spectrometry

The filter furnace atomization concept was applied for the transverse heated atomizer. A graphite filter with graphite fiber reeled onto it was inserted into the tube of the standard transverse heated graphite atomizer (THGA) in the place of the platform. Automatic plugging of the sampling hole was applied during the atomization stage. The performance of the filter atomizer (THFA), compared with the THGA, was tested for the determination of Ag, As, Au, Bi, Cd, Cu, Ga, In, Mn, Pb, Sb, Se and Tl. The analytical performances of the THFA displayed some advantages in comparison with the THGA. The sampling volume varied in the range of 5–90 μl, while drying time for any volume was less than half of that used for the THGA. Owing to the reduced diameter of the analytical zone (2 mm) along the filter axis, a sensitivity improvement was observed for all elements, 1.3–2.8-fold without plugging and 4.3–4.8-fold for Bi, Cd, Pb and Tl with plugging of the dosing hole. An increased peak width (by two to five times for the elements tested) limited the determination of less-volatile metals. The intensity of light decreased by 20–30% in comparison with the THGA. Taking into account the sensitivity, sampling volume, light loss and signal width, the calculated gain in relative detection limit is substantial (about 2.5–7 times) only for volatile elements when the plugging is applied. The pyrolysis temperatures for Ag, As, Au, Cd, Cu and Se in the THFA without addition of modifier were by 200–600°C higher than in the THGA using Pd/Mg modifier. The lifetime of THFA tubes was similar to that of THGA tubes.     

Graphite furnace atomic emission spectrometry with platform atomization

The effect of inserting a pyrolytic graphite platform into a heated graphite atomizer HGA-2100 on the atomic emission of Mo, V, Al, Ni, Cu, Cr, Mn, Zn and Cd has been studied. A comparison of calibration curves obtained with and without the use of the platform showed that although the linear dynamic range is diminished by the use of the platform, atomic emission intensities are increased by as much as 23.5 times in the most favourable case (Al) studied.Whereas no detectable net emission signal could be obtained from 5.0 × 10^?9 kg of Zn and Cd atomized from the graphite tube wall, atomization and emission from the platform yielded limits of detection: 2.7 × 10^?12 kg for Zn and 4.0 × 10^?12 kg for Cd.     

玻碳材料作平台的石墨炉原子吸收光谱研究

使用形影不离碳材料作热解涂层石墨管的恒温平台，利用玻碳材料抗化学腐蚀能力强、使用寿命长和孔隙率低等特点，克服了玻碳管使用温度受电源装置的限制及影响中等蒸发元素测定等问题。初步研究了典型易蒸发元素Ｃｄ和中等蒸发元素Ｃｕ在玻璃平台上的分析性能；比较了不同规格玻璃碳平台与标准石墨平台间的差异以及它们之间抗基体干扰的能力；用扫描电子显微镜观察了它们的表面状态。     

The design and development of a multichannel atomic absorption spectrometer for the simultaneous determination of trace metals in hair

A multichannel atomic absorption spectrometer capable of analysing up to nine elements simultaneously in human hair has been designed. Light from an array of hollow-cathode lamps is passed through an electrically heated graphite tube into a direct reading spectrometer. The photomultiplier output is fed into a novel transient signalprocessing device which separates the absorption pulse from the continuous background and increases linear range and sensitivity. Solutions containing Ni, Co, Si, Mn, Al, Cu, Ag, Cr and Fe in nanogram and sub-nanogram amounts can be determined with reasonable precision.     

Electrothermal atomization from metallic surfaces: Part 1. Design and Performance of a tungsten-tube atomizert

A tungsten-tube atomizer has been developed and tested for a number of elements. The atomizer can be accommodated in the support of a commercial Varian carbon rod atomizer (CRA-63 or CRA-90) and operated as an alternative to the graphite tubes and cups. Characteristic concentrations, detection limits, optimum atomization temperatures, reproducibility and profiles of calibration curves obtained for Ag, Al, Ba, Cd, Co, Cu, Mg, Mn, Ni, Pb and V are similar to those obtained with the graphite-tube atomizer. The main advantage of this atomizer is its simple construction, low cost, long lifetime and excellent analytical performance, particularly for elements forming refractory carbides.     

Use of laser-excited atomic fluorescence spectrometry with a novel diffusive graphite tube electrothermal atomizer for the direct determination of silver in sea water and in solid reference materials

Laser-excited atomic fluorescence spectrometry is used with a novel diffusive graphite tube electrothermal atomizer for the determination of silver in sea water and three National Institute of Science and Technology (NIST) soil reference materials (SRM 2709, 2710 and 2711). The samples are contained in a small graphite boat which is attached to one of two graphite electrodes. The boat is inserted into the center of a graphite tube which is then sealed by the electrodes and heated. The vaporized sample diffuses through the heated graphite walls and is excited by a laser beam which passes a few mm above the tube. The seawater matrix causes a two-fold suppression in the silver fluorescence signal compared with a pure aqueous standard of the same concentration. The depression is constant over a concentration range of 6 orders of magnitude. When aqueous standards were used for the determination of Ag in the solid samples, no significant difference between the measured values and the certified values were found. A limit of detection of 40 fg (4 ppt) was obtained for pure aqueous solutions and 90 fg (9 ppt) in a 1:1 diluted seawater matrix. A concentration of silver of 14 ng L⁻¹ was determined in a sample of coastal Atlantic water.     

A kinetic study of diffusion in the electrothermal atomizer with a graphite filter by laser excited atomic fluorescence

Laser excited atomic fluorescence-electrothermal atomizer (LEAFS-ETA) was used to study atomization and diffusion mechanisms in a novel diffusive graphite tube atomizer. The atomizer design included a hollow graphite cylinder mounted between two graphite rods which served as electrodes. One of the rods had a small graphite insert with a sampling hollow and could move backwards and forwards. After the sample was introduced into the hollow, the electrodes tightly sealed the graphite cylinder ensuring that the insert was directly in the center of the furnace. The furnace assembly was then heated and the vaporized sample diffused through the hot graphite wall. The atomic fraction of the sample vapor was excited by a laser beam which was directed along the graphite tube surface so that no gap remained between the beam and the tube surface. Fluorescence vs. time profiles for three elements — Cu, Ag and Ni — were obtained within the temperature range of 1400–2600 K. The rate constants of specific processes were measured from the decay portions of the fluorescence signals under the assumption of first-order kinetics. The Arrhenius plots were constructed and the activation energies, E_a were evaluated from their slopes. The plots obtained for Cu and Ag consisted of two linear parts, the corresponding values of E_a were: 195 kJ/mol and 77 kJ/mol for Cu (1550 K < T < 2600 K) and 238 kJ/mol and 97 kJ/mol for Ag (1430 K < T < 2280 K). The Arrhenius plot for Ni was linear within the temperature range of 1770–2530 K resulting in an E_a equal to 161 kJ/mol. The diffusion coefficients were evaluated on the basis of a steady-state diffusion model out of a hollow cylinder. The values for the diffusion coefficients were: 3.7·10⁻⁴−2.0·10⁻³ cm²/s (1750–2600 K) for Cu, 6.5·10⁻³−1.4·10⁻³ cm²/s (1750–2280 K) for Ag and 5.6·10⁻⁵−1.5·10⁻³ cm²/s (1770–2530 K) for Ni.     

Determination of the temperature of the graphite probe surface in graphite probe furnace atomic absorption spectrometry

An apparatus for determining the temperature of a graphite probe in graphite probe furnace atomic absorption spectrometry has been developed and tested. By measuring the change in the reflection of a laser beam from various pure metals which are deposited on the probe surface at the usual location for sample deposition, it has been found that the heating of the graphite probe surface occurs in two stages. When the probe is inserted into a pulse-heated, commercial graphite furnace after it has been heated to a steady-state temperature, the probe surface is initially rapidly heated by the radiation from the heated graphite tube wall, and thereafter the probe maintains that steady-state temperature for a short time. For a given graphite probe, the heating rate at the initial stage and the corresponding steady-state temperature at the final stage are mainly determined by the final tube wall temperature; the steady-state temperature of the probe is considerably lower than the final tube wall temperature because of thermal conduction by the probe to that part of its body which is lying outside the tube wall. The higher the final tube wall temperature, the higher is the heating rate of the probe at the initial stage, the higher is its steady-state temperature at the final stage, and the less is the difference between the final tube wall temperature and the steady-state temperature of the probe surface. The heating rate of the probe surface at 1600 K is 180 K s⁻¹, whereas at 2300 K it is 3600 K s⁻¹; the differences between the probe surface and tube wall temperatures at the former temperature is 700 K, whereas at the latter temperature it is 250 K.     

缝管原子捕集法中的原子化机理

本文用Ｘ射线衍射分析法研究了１１个元素在开缝石英管中原子捕集与释放机理。Ａｇ和Ｂｉ以金属形式被捕集，而Ｃｄ、Ｃｕ、Ｉｎ、Ｎｉ、Ｓｂ、Ｚｎ、Ｐｂ、Ｃｏ、Ｇａ则以氧化物或硅酸盐形式捕集。这些元素在放时直接从熔融物蒸发原子化。５％乙醇或丙酮能提高大多数元素的灵敏度。大多数元素在Ａｌ２３涂层管上的灵敏度较高，在Ｌａ２Ｏ３涂层管上的检出限较低，精密度较高。