Determination of phosphorus in steel with a stabilized-temperature graphite furnace and zeeman-corrected atomic absorption spectrometry

The determination of phosphorus in steel by graphite furnace a.a.s. is plagued by a spectral interference from the iron matrix which results in overcompensation when a continuum-source background corrector is used. Zeeman background correction using an alternating transverse magnetic field at the furnace eliminates this problem and allows a routine determination of phosphorus down to 0.002% in steel. Lanthanum is an effective matrix modifier for the phosphorus determination, but its enhancing effect depends largely upon the tube material used and the sample matrix. A 0.2% lanthanum solution was found to be optimum. The stabilized-temperature platform furnace concept allows an interference-free determination of phosphorus in steel, down to 0.002%, directly against aqueous standards. Atomizing the sample from a pyrolytic graphite platform in an uncoated graphite tube provides the optimum environment for a phosphorus determination.     

Optimization of the determination of selenium in marine samples by atomic absorption spectrometry: Comparison of a flameless graphite furnace atomic absorption system with a hydride generation atomic absorption system

A comparison has been made between a graphite furnace system based on nickel as a matrix stabilizing metal and an automated hydride generation system with a heated quartz cell. The effect of nickel as a matrix modifier was studied in pure selenite solutions as well as in biological matrixes by different charring temperatures. The suppression effect of different acids on the response of the analyte is reported and discussed. The use of an electrically heated quartz tube as an alternative to the argon hydrogen flame method unproved the selenium determination by hydride generation atomic absorption. The effect of hydrochloric acid to secure quantitative formation of selenium (IV) and the interference of copper in the response measurements have been studied. Further a comparison has been made between three different digestion procedures when the hydride generation atomic absorption system was applied. The results of the graphite furnace atomic absorption and the hydride generation atomic absorption were found to be equally accurate, but the graphite furnace technique gave better reproducibility.     

Determination of mercury in environmental samples by cold vapour generation and atomic-absorption spectrometry with a gold-coated graphite furnace

Mercury is determined at below the pg/ml level by a combination of cold vapour generation, trapping in a gold-coated graphite furnace and atomic-absorption detection. The mercury is reduced to the element by stannous chloride, stripped from solution by a stream of nitrogen and collected on a gold-coated porous graphite disk in a graphite furnace. It is then atomized by increasing the graphite furnace temperature and detected by an atomic-absorption spectrophotometer. The absolute detection limit and the characteristic mass were found to be 5 and 20 pg for 0.0044 absorbance, respectively. The concentration limit of detection was 0.1 pg/ml for a 50-ml sample, and the linear dynamic range covered three orders of magnitude. The precisions of the measurements were 2.7% for 0.1 ng and 2.6% for 2 ng of mercury. Analyses of NBS and NIES reference materials showed quantitative recovery. Analytical results obtained by the technique are presented for natural waters, marine biota and sediments.     

Temporal Variations in Gas Temperature in an Atomization Stage of Cadmium and Tellurium Evaluated by Using the Two-line Method in Graphite Furnace Atomic Absorption Spectrometry

In order to discuss the atomization process of an analyte element occurring in a graphite furnace for atomic absorption spectrometry, we measured variations in the characteristic temperature with the progress of an atomization stage, by using a two-line method under the assumption of a Boltzmann distribution. For this purpose, iron was chosen as the analyte element. Also, the atomic absorption of two iron atomic lines, Fe I 372.0 nm and Fe I 373.7 nm, was simultaneously monitored as a probe for the temperature determination. This method enables variations in the gas temperature to be directly traced, yielding a temperature distribution closely related to the diffusion behavior of the probe element in the furnace. This temperature variation was very different from the furnace wall temperatures, which were monitored in conventional temperature control for atomic absorption spectrometry. Correlations between the gas temperature and the charring/atomizing temperatures in the heating program of the furnace were investigated. The atomization of cadmium and tellurium was also investigated by a comparison between the gas temperature with the wall temperature of the furnace. The atomic absorption of cadmium or tellurium appeared to be apart from the absorption of iron while the gas temperature was still low. Therefore, the analyte atoms could be atomized through direct contact with the wall of the graphite furnace, which has a much higher temperature compared to the gas atmosphere during atomization. Their atomization would be caused by conductive heating from the furnace wall rather than by radiant heating in the furnace.     

Capacitive Discharge Graphite Furnace Laser-Excited Atomic Fluorescence of Thallium

For the first time, an anisotropic graphite furnace heated by capacitive discharge was used for laser-excited atomic fluorescence spectrometry. A detection limit of 5 fg for thallium was obtained with a laser repetition rate of 500 Hz and a peak integration time of 80 ms. The use of a capacitive discharge furnace allows for a shorter integration time, which in turn should allow for integration of less background noise, and improved detection limits. Theoretically, the magnitude of the shot noise should be proportional to the square root of the integration time, and inversely proportional to the square root of the laser repetition rate. Experimental data illustrated the effect of laser repetition rate, but were inconclusive with respect to integration time. The linear dynamic range of the calibration curve was six orders of magnitude, which was comparable to that normally obtained for laser-excited atomic fluorescence in modern commercial graphite furnaces. Thallium was accurately determined in NIST biological samples at levels one to two orders of magnitude below the detection limit of electrothermal atomic absorption spectrometry, with an analytical precision between 8 and 20%. The interference effects of calcium, sodium chloride, and potassium chloride on the thallium signal were investigated and shown to be similar to both laser-excited atomic fluorescence in a conventional furnace and capacitive discharge furnace atomic absorption results reported in the literature.     

The determination of manganese by electrothermal atomic absorption spectrometry with a graphite furnace at constant temperature

Many of the interferences reported earlier for the determination of manganese in a graphite furnace were not found when a modern graphite furnace was used. At high levels of chloride matrix, an interference which was observed in the modern furnace was reduced when manganese was determined under constant temperature conditions. In this work, the sample was introduced on a tungsten wire after the graphite furnace had reached a constant, preset temperature. Drying and ashing were accomplished outside the atomization furnace, reducing contamination from matrix materials.     

Semi-Automating the Operations of an HGA-2000 Furnace Used On a Perkin-Elmer Model 503 Atomic Absorption Spectrophotometer Equipped with a Peak Read Function

Abstract

A sequence relay timer is described for the automatic control of some instrument parameters when the HGA 2000 graphite furnace is employed with the Perkin-Elmer model 503 spectrophotometer equipped with a peak mode function. Its application is intended for routine trace metal analysis and provides automatic control of the instrument zero, an area integrator and a peak reader.     

Vaporization and atomization of uranium in a graphite tube electrothermal vaporizer: a mechanistic study using electrothermal vaporization inductively coupled plasma mass spectrometry and graphite furnace atomic absorption spectrometry

The mechanism of vaporization and atomization of U in a graphite tube electrothermal vaporizer was studied using graphite furnace atomic absorption spectrometry (GFAAS) and electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS). Graphite furnace AAS studies indicate U atoms are formed at temperatures above 2400°C. Using ETV-ICP-MS, an appearance temperature of 1100°C was obtained indicating that some U vaporizes as U oxide. Although U carbides form at temperatures above 2000°C, ETV-ICP-MS studies show that they do not vaporize until 2600°C. In the temperature range between 2200°C and 2600°C, U atoms in GFAAS are likely formed by thermal dissociation of U oxide, whereas at higher temperatures, U atoms are formed via thermal dissociation of U carbide.The origin of U signal suppression in ETV-ICP-MS by NaCl was also investigated. At temperatures above 2000°C, signal suppression may be caused by the accelerated rate of formation of carbide species while at temperatures below 2000°C, the presence of NaCl may cause intercalation of the U in the graphite layers resulting in partial retention of U during the vaporization step. The use of 0.3% freon-23 (CHF₃) mixed with the argon carrier gas was effective in preventing the intercalation of U in graphite and U carbide formation at 2700°C.     

石墨炉电热蒸发进样与ICP—AES联用技术研究——仪器装置及其分析性能

将石墨炉作为蒸发器与ICP－AES联用，改善其检出限并赋予微量体积样品分析的能力，用自已缓装的仪器，选择了等离子体和石墨炉各自最佳操作，结果表明，取样量为10μL时，大多数元素的检出限达μg/L级；相对标准偏差5％；线性范围达4个数量级。     

锡石墨炉原子化机理研究

本文考察了盐酸、硫酸、硝酸、亚硒酸及硼酸中锡的石墨炉原子吸收特性,对锡在不同基体中的原子化过程进行了初步探讨。发现硼酸是石墨炉法测定锡时的一种较好的化学改进剂;1%的硼酸加入可克服一定含量的硫酸与盐酸的干扰。并利用XRD与XPS对硼酸与锡共存时的石墨表面进行了结构与状态分析。提出了硼酸与锡共存时,锡的原子化历程。     

石墨探针—原子吸收光谱法测定人发中痕量铟的研究

探针原子化技术是一种实现等温原子化,改善灵敏度的行之有效的方法。本文采用此方法对痕量钿进行了一系列条件试验,峰面积与钿浓度在0～50ng·ml~(-1)范围内呈线性关系,其特征量4.8pg,检出限21.5pg,相对标准偏差5.7％,并成功地测定了成人发中铟的含量,范围在12～159pg·g~(-1),回收率96.4％～103.2％。该方法灵敏度高,操作简单、快速,结果满意。     

Direct determination of metals associated with airborne particulates using a graphite probe collection technique and graphite probe atomic absorption spectrometric analysis

A new analytical method has been developed for direct analysis of solid samples of airborne particulate matter by a graphite probe collection technique coupled with graphite furnace atomic absorption spectrometry. A porous graphite probe is used as a filter for air particles. The probe is then subjected to atomization by being inserted into a graphite furnace which has been pre-heated to a constant atomization temperature. Some aspects of the method have been tested by recovery studies using NBS Urban Particulate Matter, SR M No. 1648, and found to give recoveries of 91–107% for Pb, Cd, Ni, Cu and Mn. By combining a highly efficient filtering medium with the extremely high relative sensitivity of solid sampling, this method has the potential of monitoring sources of air particulate emission with sufficient temporal and spatial resolution for unequivocal identification of the pollution source (at least on a local scale).     

Implications of a speed dependent modified Voigt function in atomic absorption spectrometry

A speed dependent modified Voigt function (MVF) is utilized to describe atomic spectral line profiles and compared to the well known Voigt function (VF). The air—acetylene flame has been used for these comparisons. In all cases the MVF differs from the VF in the calculation of atomic absorption coefficients (up to 15%), full-width half-maximum (FWHM) intensity values (up to 18%), and a-parameter values (up to 80%). The variation between the functions is mass dependent and decreases with atomic weight. The MVF is used to evaluate published lineshape data and reveals a significant difference in calculated collisional cross section values. In addition an experimental situation is evaluated using the MVF and VF to show that the perturber gas in a graphite furnace is important due to its influence on the absorption coefficient at line center.     

Determination of lead in biological materials by constant-temperature electrothermal atomic absorption spectrometry

A comparison is made between a platform-equipped Perkin-Elmer HGA-500 and a recently designed two-step constant-temperature graphite furnace with respect to susceptibility to interference effects as well as attainable detection limits. It is shown that larger quantities of biological samples can be used with the constant-temperature furnace without suppressing the analyte signal, resulting in lower detection limits. Materials studied include NBS Olyster Tissue and Bovine Liver, and human lung tissue and human blood.     

A temperature-controlled graphite tube furnace for the determination of trace metals in solid biological tissue

A temperature-controlled graphite furnace for atomic-absorption analysis has been built and tested. The temperature of the graphite tube was monitored with an infrared-sensitive detector. Samples were introduced directly or via a separately heated graphite cup. Micro-samples of solid biological tissue were analysed directly for Zn, Mn and Co and the sensitivities for 1% absorption were 0.05,2 and 10 pg respectively. The salt content of the tissue limits the sample sizes, owing to non-specific absorption. The ashing conditions were investigated and found to be especially critical for Zn.     

Determination of total tin in geological materials by electrothermal atomic-absorption spectrophotometry using a tungsten-impregnated graphite furnace

An electrothermal atomic-absorption spectrophotometric method is described for the determination of total tin in geological materials, with use of a tungsten-impregnated graphite furnace. The sample is decomposed by fusion with lithium metaborate and the melt is dissolved in 10% hydrochloric acid. Tin is then extracted into trioctylphosphine oxide-methyl isobutyl ketone prior to atomization. Impregnation of the furnace with a sodium tungstate solution increases the sensitivity of the determination and improves the precision of the results. The limits of determination are 0.5-20 ppm of tin in the sample. Higher tin values can be determined by dilution of the extract. Replicate analyses of eighteen geological reference samples with diverse matrices gave relative standard deviations ranging from 2.0 to 10.8% with an average of 4.6%. Average tin values for reference samples were in general agreement with, but more precise than, those reported by others. Apparent recoveries of tin added to various samples ranged from 95 to 111% with an average of 102%.     

Solid sampling by electrothermal vaporization in combination with electrostatic particle deposition for electrothermal atomization multi-element analysis

A novel combination of electrothermal sample vaporization from one furnace and electrostatic deposition of the aerosol on a L'vov platform in a second graphite furnace used for subsequent electrothermal atomization multi-element analysis is described. The aerosol generated by vaporization of liquid as well as solid primary samples is transported to the graphite furnace by an Ar gas flow and is piped into the furnace through the dosing hole via a glass capillary mounted on the autosampler arm of a continuum source coherent forward scattering spectrometer. The deposition on the graphite platform is obtained electrostatically by a corona-like discharge. The near quantitative deposition of the produced and transported aerosol allows optimal direct determination of the transport efficiencies by comparing the signals obtained by measuring liquid samples directly with the spectrometer with signals obtained with samples transferred with electrothermal vaporization and electrostatic deposition. Over all transfer efficiencies up to 30% are observed with liquid primary samples. Results obtained with solid sampling of BCR CRM 189 Wholemeal flour are in good agreement with the certified values.     

微波消解-石墨炉原子吸收光谱法测定纳米二氧化钛中痕量砷

建立了微波消解-石墨炉原子吸收光谱法（GF-AAS）测定纳米二氧化钛中痕量杂质元素砷的分析方法。采用由一定浓度和比例的氢氟酸、硝酸组成的混合试剂,结合应用高压密闭微波加热技术快速完全消解纳米二氧化钛样品,优选了最佳微波加热控制程序,不仅解决了二氧化钛难消解和待测元素砷高温消解过程中易挥发损失等难点,而且检测溶液酸度低,避免对GF-AAS石墨管的侵蚀。并且,通过基体效应影响实验,优化选择了石墨管类型、石墨炉升温原子化控制程序以及原子吸收光谱仪检测参数,消除热稳定性强的二氧化钛基体对测定易挥发痕量元素砷的影响。方法检出限为0.02μg/L,加标回收率为93.0%~106.0%,相对标准偏差9.4%,与ICP-MS检测方法结果对照一致。