Tomographically resolved ionization temperatures and electron densities in the inductively coupled plasma determined by the line-to-continuum method

This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by three disks with data files with the hardcopy paper in Word 5.0 and ASCII format, and a disclaimer. The text details the purpose of the work and the structure of the three-dimensional Ar ionization temperature and electron number density data files. The line-to-continuum method was used to evaluate the spatial distribution of Ar ionization temperatures, T_ion, and electron number densities, n_e, within a dry Ar inductively coupled plasma (ICP). The emission measurements were spatially resolved in three dimensions by reconstruction algorithms for computed tomography. The 40.68 MHz Ar ICP was operated at applied r.f. power levels of 0.75 and 1.0 kW. The reconstructed distributions of Ar I line emission (430.0 nm) and continuum emission (428.6 nm) show good reproducibility over a series of five replicate runs. Argon ionization temperatures remain within a 6500–8500 K range throughout the continuum-emission cone of the plasma. Deviations from this temperature range occur in the central channel and around the outer edge of the plasma. Low in the plasma, the central-channel T_ion is cooler than 6000 K. Along the outer edge of the plasma, the line-to-continuum ratio becomes small; this low ratio results in erroneously high temperatures (> 12000 K). The errors in T_ion appear to be due to reproducible artifacts in the reconstruction process that lead to low Ar I line-emission readings along the outer edge of the plasma. Electron densities show a maximum of 8.5 × 10¹⁴ cm⁻³ and 1.2 × 10¹⁵ cm⁻³ at 0.75 and 1.0 kW, respectively. Electron number densities were much better behaved than T_ion due to their dependence on the square-root of continuum measurements and only the fourth-root of T_ion.     

Comparison of simulated and experimental fundamental ICP parameters

False-color spatial maps of experimentally determined and simulated values of electron number density (n_e), electron temperature (T_e) and heavy-particle temperature (T_g) for an argon inductively coupled plasma (ICP) in the plasma decay region (tail flame) are compared in detail. Experimental and theoretical values are in general very consistent; the difference between experiment and computation is approximately 10% for n_e and T_e and 20% for T_g in the plasma region examined. The errors in n_e and T_e are larger at the edge of the plasma, most likely because air entrainment becomes significant. This comparison provides a link between measurements and the current mathematical model and serves to partially validate both methods. Sources of error in both experiment and theory are considered and discussed.     

An evaluation of ion-atom emission intensity ratios and local thermodynamic equilibrium in an argon inductively coupled plasma

Spatially resolved, radial electron density (n_e) profiles have been measured at rf power settings of 0.75, 1.25 and 1.75 kW, and vertical heights of 4,8,12,16,20 and 24 mm above the load coil. These measured values of n_e have been used to construct a theoretical local thermal equilibrium (LTE) framework. Ion-atom emission intensity ratios for Mg and Cd calculated from this framework have been compared to experimentally measured values. The measured ion-atom emission intensity ratios are found to be (ess than calculated LTE ratios. This suggests that the aerosol channel of the inductively coupled plasma can be characterized as an ionizing plasma.     

Detection limits for lines widely differing in “hardness” and intensity ratios of ionic to atomic lines measured in 50 and 100 MHz inductively coupled plasmas

Using the same torch and nebulizer, a 50 and a 100 MHz inductively coupled plasma (ICP) with argon as working gas were rationally optimized to achieve maximum detection power. The detection limits (actually source SBRs) of 55 elements were measured in both ICPs under the respective compromise conditions using 84 spectral lines, comprising 30 atomic and 54 ionic lines. These detection limits did not differ essentially and therefore it appeared likely that the excitation conditions did not differ substantially either. It was considered whether this feature was reflected in the changes of the ratios of the intensities of ionic to atomic lines derived from the same set of measurements. A rational interpretation of the results in terms of Saha-Boltzmann relationships led to the conclusion that the changes in the ionic to atomic line intensity ratios could reflect closely similar excitation conditions only if a rigorous LTE coupling between the (electron) temperature (T) and the electron concentration (n_e) was precluded, in other words, the results pointed to the likelihood of a model in which T and n_e vary independently, n_e in fact being assumed constant within the range of conditions under consideration (T = 6300 ± 300 K). On the whole, the conclusions should be treated with caution, since no Abel inversion has been applied. However, the approach as such may be of interest as a basis for more rigorous experiments.     

Plasma behavior during electrothermal vaporization sample introduction in inductively coupled plasma atomic emission spectrometry

Electrothermal vaporization (ETV) sample introduction in inductively coupled plasma atomic emission spectrometry suffers from severe matrix effects. In the present study, the differences between wet and dry plasma conditions are studied. In addition, the influence of the sample composition was investigated. An inductively coupled plasma optical emission spectrometer, with detection based on charge transfer, allowed the simultaneous measurement of ionic and atomic emission line intensities during the transient signal. Mg and Cr were the test elements. The ion-to-atom line ratio increases at higher power settings, but the changes were larger when a nebulizer was used for sample introduction than with ETV sample introduction. The decrease of ion-to-atom line ratios at increasing observation height was more pronounced when ETV was used, due to the absence of water vapor. The gas flow rate showed a stronger influence for nebulization than for ETV. In the presence of a calcium matrix, lower ion-to-atom line ratios were observed, but the ratio did not change significantly within the transient emission signal. Similar line ratios were observed for different amounts of calcium matrix. The values of ion-to-atom line ratios for Mg and Cr indicate that the plasma ionization and thermal characteristics are not modified due to the presence of the calcium matrix.     

An experimental study of asymmetry in an argon inductively coupled plasma torch using a relaxation method

A relaxation method is used to undertake an experimental study of the degree of cylindrical symmetry present in an argon inductively coupled plasma torch, ICP. This technique, in effect a direct comparison between two different parameters, the electron (T_e) and gas (T_g) temperatures in the torch, is shown to be a very sensitive indicator of axisymmetry. Measurements using this technique delineate areas of axisymmetry in the ICP, and show that axisymmetry is significantly dependent on the observation height and coolant gas flow-rate.     

Tungsten devices in analytical atomic spectrometry

Tungsten devices have been employed in analytical atomic spectrometry for approximately 30 years. Most of these atomizers can be electrically heated up to 3000 °C at very high heating rates, with a simple power supply. Usually, a tungsten device is employed in one of two modes: as an electrothermal atomizer with which the sample vapor is probed directly, or as an electrothermal vaporizer, which produces a sample aerosol that is then carried to a separate atomizer for analysis. Tungsten devices may take various physical shapes: tubes, cups, boats, ribbons, wires, filaments, coils and loops. Most of these orientations have been applied to many analytical techniques, such as atomic absorption spectrometry, atomic emission spectrometry, atomic fluorescence spectrometry, laser excited atomic fluorescence spectrometry, metastable transfer emission spectroscopy, inductively coupled plasma optical emission spectrometry, inductively coupled plasma mass spectrometry and microwave plasma atomic spectrometry. The analytical figures of merit and the practical applications reported for these techniques are reviewed. Atomization mechanisms reported for tungsten atomizers are also briefly summarized. In addition, less common applications of tungsten devices are discussed, including analyte preconcentration by adsorption or electrodeposition and electrothermal separation of analytes prior to analysis. Tungsten atomization devices continue to provide simple, versatile alternatives for analytical atomic spectrometry.     

Identification of Oil Pollution Sources by a Set of Modern Instrumental Methods

Source of contamination of the soil and water with oil can be exactly identified by a set of instrumental methods such as atomic absorption spectrometry, inductively coupled plasma mass spectrometry, atomic emission spectroscopy, X-ray fluorescence analysis, and inductively coupled plasma emission spectrometry.     

Trace characterization of high-purity molybdenum and tungsten by electrothermal atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry and total reflection X-ray fluorescence spectrometry involving analyte—matrix separation

A technique for the separation of 42 trace elements from up to 5 g of molybdenum and tungsten matrices was developed by means of the radiotracer technique. It is based on adsorption of the analyses on the cation exchanger Dowex 50 W x 9 from a 4% H₂O₂/0.01 mol 1⁻¹ HNO₃ solution followed by their elution with 15 ml of 4 mol I⁻¹ HNO₃ in the opposite flow direction. Both matrices were removed with a separation factor > 10⁴. The separation technique was applied to the analysis of these materials by electrothermal atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry and total reflection X-ray fluorescence spetrometry. For all the determination methods used, the limits of detection are given and compared with those of other methods. With inductively coupled plasma mass spectrometry, for 22 of the 30 assayed elements, limits of detection at the sub-ng g⁻¹ level were achieved. The results are compared with those obtained by radiochemical neutron activation analysis in this work and by glow discharge mass spectrometry, secondary ion mass spectrometry, isotope dilution mass spectrometry and by solution spectrometric methods in other laboratories.     

The influence of the sample introduction system on signals of different tin compounds in inductively coupled plasma-based techniques

The influence of the sample introduction system on the signals obtained with different tin compounds in inductively coupled plasma (ICP) based techniques, i.e., ICP atomic emission spectrometry (ICP–AES) and ICP mass spectrometry (ICP–MS) has been studied. Signals for test solutions prepared from four different tin compounds (i.e., tin tetrachloride, monobutyltin, dibutyltin and di-tert-butyltin) in different solvents (methanol 0.8% (w/w), i-propanol 0.8% (w/w) and various acid matrices) have been measured by ICP–AES and ICP–MS. The results demonstrate a noticeable influence of the volatility of the tin compounds on their signals measured with both techniques. Thus, in agreement with the compound volatility, the highest signals are obtained for tin tetrachloride followed by di-tert-butyltin/monobutyltin and dibutyltin.The sample introduction system exerts an important effect on the amount of solution loading the plasma and, hence, on the relative signals afforded by the tin compounds in ICP–based techniques. Thus, when working with a pneumatic concentric nebulizer, the use of spray chambers affording high solvent transport efficiency to the plasma (such as cyclonic and single pass) or high spray chamber temperatures is recommended to minimize the influence of the tin chemical compound. Nevertheless, even when using the conventional pneumatic nebulizer coupled to the best spray chamber design (i.e., a single pass spray chamber), signals obtained for di-tert-butyltin/monobutyltin and dibutyltin are still around 10% and 30% lower than the corresponding signal for tin tetrachloride, respectively. When operating with a pneumatic microconcentric nebulizer coupled to a 50 °C-thermostated cinnabar spray chamber, all studied organotin compounds provided similar emission signals although about 60% lower than those obtained for tin tetrachloride. The use of an ultrasonic nebulizer coupled to a desolvation device provides the largest differences in the emission signals, among all tested systems.     

电感耦合等离子体质谱法测定黄沙土壤中铅同位素比

用电感耦合等离子体质谱法（ＩＣＰ—ＭＳ）测定了５个黄沙原土样品中铅同位素比２０７Ｐｂ／２０６Ｐｂ、２０８Ｐｂ／２０６Ｐｂ，样品来自被认为是黄沙气溶胶源地区，为了使铅同位素测量中质量偏差和漂移减至最少，在样品中加入了铊标准溶液，测量２０５Ｔｌ／２０３Ｔｌ比，校正质量数差别选择的影响．同时，采用ＩＣＰ—ＭＳ和电感耦合等离子体原子发射光谱法（ＩＣＰ一ＡｌＳ）测定了随粒径变化样品中１２种元素浓度的变化．     

New developments in thermospray sample introduction for atomic spectrometry

The status of thermospray sample introduction for analytical atomic spectrometry was last reviewed in 1992. In this review, we summarize developments in this field since that time, including investigations of aerosol generation processes, noise diagnosis and control with inductively coupled plasma-atomic emission or mass spectrometry (ICP-AES/MS), high flow thermospray, the use of dual-stage desolvation systems based on membrane dryers, and the utilization of thermospray with axially viewed ICP-AES. Since a major advantage of methods based on thermospray is improved limits of detection, the emphasis for applications of thermospray with ICP spectrometries remains focused on environmental sample types, particularly with ICP-MS. Relatedly, the use of thermospray as a means for the direct speciation of Se is also under development.     

Multi-element characterization of silicon nitride powders by atomic and mass spectrometric solution methods

A sample pretreatment technique for silicon nitride involving digestion and matrix/traces separation was developed by means of radiotracers and applied to analysis of this material by inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry and graphite furnace atomic absorption spectrometry. The results obtained for a high purity silicon nitride material by these methods are compared each with the other and with those obtained by neutron activation analysis. The limits of detection and the capabilities of the methods are compared and discussed.     

Determination of metals in biofluids and tissues: sample preparation methods for atomic spectroscopic techniques

Several sample preparation methods unique to each instrumental technique exist for the elemental analysis of biological specimens, but no review or book has dealt with them. The present review is an attempt to fill this void and focuses on sample preparation methods unique to atomic and X-ray spectroscopic techniques. The techniques covered are: flame and electrothermal AAS, inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS) and X-ray fluorescence spectrometry (XRF) since these are most commonly used in trace element analysis of biological materials. The intent is not to present the procedural details for the various tissues or elements, but rather to highlight the methods which are unique to each instrument. The bibliography accompanying this review should aid the analytical chemist in his/her search for the detailed preparation protocols.     

通过脱碳控制全球平均温度

Establishing a reliable method to predict the global mean temperature (T_e) is of great importance because CO₂ reduction activities require political and global cooperation and significant financial resources. The current climate models all seem to predict that the earth's temperature will continue to increase, mainly based on the assumption that CO₂ emissions cannot be lowered significantly in the foreseeable future. Given the earth's multifactor climate system, attributing atmospheric CO₂ as the only cause for the observed temperature anomaly is most likely an oversimplification; the presence of water (H₂O) in the atmosphere should at least be considered. As such, T_e is determined by atmospheric water content controlled by solar activity, along with anthropogenic CO₂ activities. It is possible that the anthropogenic CO₂ activities can be reduced in the future. Based on temperature measurements and thermodynamic data, a new model for predicting T_e has been developed. Using this model, past, current, and future CO₂ and H₂O data can be analyzed and the associated T_e calculated. This new, esoteric approach is more accurate than various other models, but has not been reported in the open literature. According to this model, by 2050, T_e may increase to 15.5 ℃ under "business-as-usual" emissions. By applying a reasonable green technology activity scenario, T_e may be reduced to approximately 14.2 ℃. To achieve CO₂ reductions, the scenario described herein predicts a CO₂ reduction potential of 513 gigatons in 30 years. This proposed scenario includes various CO₂ reduction activities, carbon capturing technology, mineralization, and bio-char production; the most important CO₂ reductions by 2050 are expected to be achieved mainly in the electricity, agriculture, and transportation sectors. Other more aggressive and plausible drawdown scenarios have been analyzed as well, yielding CO₂ reduction potentials of 1051 and 1747 gigatons, respectively, in 30 years, but they may reduce global food production. It is emphasized that the causes and predictions of the global warming trend should be regarded as open scientific questions because several details concerning the physical processes associated with global warming remain uncertain. For example, the role of solar activities coupled with Milankovitch cycles are not yet fully understood. In addition, other factors, such as ocean CO₂ uptake and volcanic activity, may not be negligible.     

Indirect measuring method of aerosol transport efficiency in inductively coupled plasma spectrometry

Summary An indirect method developed for measuring the aerosol transport efficiency in inductively coupled plasma spectrometry using a conventional sample introduction system composed of concentric nebulizer/spray chamber/torch is described. The precision of this simple method is within 5% in terms of the relative standard deviation for the 23 °C distilled water with argon carrier gas flow rates of 0.6 to 1.4 l/min.

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Indirektes Meßverfahren für das Transportvermögen des Aerosols bei der ICP-Spektrometrie

     

Influence of the operating parameters and of the sample introduction system on time correlation of line intensities using an axially viewed CCD-based ICP-AES system

The influence of the acquisition and operating parameters on time correlation between emission line intensities was investigated using axially viewed inductively coupled plasma-multichannel-based emission spectrometry and various sample introduction systems.     

Some observations on electrothermal vaporisation for sample introduction into the inductively coupled plasma

The development and analytical utility of electrothermal vaporisation techniques employing a graphite rod for sample introduction into the inductively coupled plasma (ICP) are assessed. In most instances detection limits are superior to those obtained with nebulisation based systems, and are comparable to those obtained with graphite furnace atomic absorption spectrometry. A model is derived for the sample injection process. Additionally the major interference and alteration of the plasma excitation phenomena ensuing from the sample introduction of a solvent free aerosol are discussed in order to assess the analytical potential of the technique for routine μl volume sample introduction in ICP spectrometry. The capability for simultaneous multi-element analyses is maintained with the electrothermal vaporisation technique.     

Spectrochemical determination of trace As, Fe, Hg, Mn, and Pb by an argon-stabilized U-shaped DC arc

Argon-stabilized U-shaped DC arc with a system for aerosol introduction was used for the determination of As, Fe, Hg, Mn, and Pb. By applying a computer program performing a time integration of the registered signals and by optimizing the working conditions of an U-shaped arc plasma, the detection capability for As, Fe, Hg, Mn, and Pb was improved, which contributed to the lowering of the detection limits. The lowest detection limits for Fe, Mn, and Pb were achieved during an integration time of 20 s, and for As and Hg during an integration time of 30 s, and their values were 1.1, 0.1, 0.9, 15, and 2.6 ng/mL, respectively. The detection limits obtained by our method with optimal integration times were compared with the detection limits obtained using other methods: inductively coupled plasma-atomic emission spectrometry (ICP-AES), directly coupled plasma-atomic emission spectrometry (DCP-AES), microwave-induced plasma-atomic emission spectrometry (MIP-AES), inductively coupled plasma-mass spectrometry (ICP-MS), and an improved thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS). The text was submitted by the authors in English.     

Matrix effects in inductively coupled plasma mass spectrometry: a review

Fundamental research on non-spectroscopic interferences, also known as matrix effects, in inductively coupled plasma (ICP) mass spectrometry with sample introduction using nebulization is critically and exclusively examined in this review, starting with fundamental processes that may be a source of matrix effects during sample introduction, ion generation in the ICP, ion extraction through the interface, and ion transport through the ion optics to the detector. Various methods for attenuating matrix effects are then reviewed and illustrated with some examples. Instead of exhaustively reviewing the literature, representative references are used to comprehensively describe the main issues, several of which are also common to ICP optical emission spectrometry.