Characterization of an annular helium inductively coupled plasma generated in a low-gas-flow torch

Atomic emission detection limits of Br, C, Cl and I measured for gaseous and aqueous samples with a low-gas-flow, annular He ICP were lower than those obtained with an Ar 1CP. Measurements of electron number density, excitation temperature and rotational temperature revealed that the extent of departure from local thermal equilibrium for the He ICP was larger than that for the Ar ICP.     

Evaluation of sample preparation methods for elastomer digestion for further halogens determination

In this work, three sample preparation methods were evaluated for further halogen determination in elastomers containing high concentrations of carbon black. Samples of nitrile-butadiene rubber, styrene-butadiene rubber, and ethylene-propylene-diene monomer elastomers were decomposed using oxygen flask combustion and microwave-induced combustion (MIC) for further Br and Cl determination by ion chromatography (IC), inductively coupled plasma optical emission spectrometry (ICP OES), and inductively coupled plasma mass spectrometry (ICP-MS). Extraction assisted by microwave radiation in closed vessels was also evaluated using water or alkaline solution. Digestion by MIC was carried out using 50 mmol l⁻¹ (NH₄)₂CO₃ as the absorbing solution. The effect of the reflux step was also evaluated. Accuracy was evaluated using certified reference materials with polymeric matrix composition and by comparison of results using neutron activation analysis. Agreement for Br and Cl was better than 95% by MIC using 5 min of reflux, and no statistical difference was found using IC, ICP OES, and ICP-MS for determination of both analytes. For MIC, the relative standard deviation (RSD) was lower than 5%. Using extraction in closed vessels, a high amount of residues was observed, and recoveries were lower than 45% for both analytes. For oxygen flask combustion, the agreement was similar using MIC but RSD was higher (20%). The residual carbon content, an important parameter used to evaluate the digestion efficiency, was always below 1% for MIC. Using MIC, it was possible to digest elastomers with high efficiency, resulting in a single solution suitable for halogen determination by different techniques.     

A status report on helium inductively coupled plasma mass spectrometry

The current status of helium inductively coupled plasma - mass spectrometry (He ICPMS) is examined, its potentials and limitations are reviewed, and a summary of fundamental properties of atmospheric pressure He ICP discharges is presented. Also included are results of He ICPMS studies with a new helium plasma torch (18 mm i.d.) operated at four sets of operating conditions. Under the "cold plasma" condition (600 W forward power), no secondary discharge is observed and ion kinetic energies ranging from 2.0 eV to 9.5 eV for 6 elements (mass range: 39-208) are measured. At higher power levels, the secondary discharge still is strong. In general, detection limits for certain elements are improved by 1-3 orders of magnitude compared to previous data acquired in 1993 with a 13-mm He ICP torch. Elements such as K, Fe, Cr, Mn, Ni, and Co that suffer from spectral interferences in Ar ICPMS can be detected at pg/mL-levels with an analogue detector and a prototype ICPMS instrument having no photon stops or obstacles present in the ion trajectory path.     

Experimental studies for the characterization of analytical performance in axially-observed inductively coupled plasma atomic emission spectrometry

Investigations were carried out on the optimization of excitation and projection conditions of the axially-observed inductively coupled plasma (ICP) concerning simultaneous measurements. For minimized background equivalent concentration (BEC) it can be shown that the optimal excitation conditions of the atomic and ionic lines also vary in the case of axial plasma observation. A relationship was confirmed between the high frequency power and the excitation energy of the analytical lines. The main contribution of this work is the displacement of the axial viewing inductively coupled plasma by means of an x,y,z sliding carriage.The displacement showed that under the selected experimental conditions the point of observation is spatially identical for all analytical lines. Received: 30 May 1997 / Revised: 20 November 1997 / Accepted: 25 November 1997     

Experimental studies for the characterization of analytical performance in axially-observed inductively coupled plasma atomic emission spectrometry

Investigations were carried out on the optimization of excitation and projection conditions of the axially-observed inductively coupled plasma (ICP) concerning simultaneous measurements. For minimized background equivalent concentration (BEC) it can be shown that the optimal excitation conditions of the atomic and ionic lines also vary in the case of axial plasma observation. A relationship was confirmed between the high frequency power and the excitation energy of the analytical lines. The main contribution of this work is the displacement of the axial viewing inductively coupled plasma by means of an x,y,z sliding carriage.The displacement showed that under the selected experimental conditions the point of observation is spatially identical for all analytical lines. Received: 30 May 1997 / Revised: 20 November 1997 / Accepted: 25 November 1997     

Comparison of temperature measurements in ICP and MIP with Ar and He as plasma gas

Various temperature measurements have been carried out in microwave induced plasmas (MIP) generated with a surfatron and inductivcly coupled plasmas (ICP) both with argon and helium as plasma gas. Iron has been used for the determination of excitation temperature, and OH and N⁺₂ for rotational temperatures. In the case of the Ar ICP, equilibrium is attained between the various temperatures (4500 K), as previously described. On the other hand, in the He ICP and the MIPs, iron provides the highest temperature (4500 K) but discrepancies are obtained with results from N⁺₂ and OH. These two species show lower values, especially OH (2000 K).     

Spatial profile measurement of ionization and excitation temperatures in an inductively coupled plasma

The developed instrument for spatial profile measurement [1] has been applied to the measurement of ionization and excitation temperatures in an inductively coupled plasma (ICP). The silicon intensified target (SIT) detector allowed it to measure a large number of emission spectra in a short period. The ease of acquisition enabled building up complete contour maps of ionization and excitation temperatures. The contour maps of various temperatures reveal that local thermal equilibrium does not exist in the whole ICP. The comparison between ionization temperature profiles for Ar and Ca indicates that in the normal analytical zone of the ICP, Ca is ionized as expected from the Ar ionization temperature. Excitation temperatures derived from low-level Fe I lines are lower than those derived from high-level Fe I lines over a large part of the plasma. The result confirms that for Fe I lines the ICP is characterized as an ionizing plasma in the whole ICP and the low atomic levels are overpopulated with respect to the high atomic levels.     

Mixed-gas inductively coupled plasma atomic emission spectrometry using a direct injection high efficiency nebulizer

Experimental studies and computer simulations were conducted to identify plasma operating conditions and to explore and contrast the excitation conditions of Ar, Ar-O2, and Ar-He inductively coupled plasmas (ICPs) for the introduction of microliter volumes of sample solutions with a direct injection high efficiency nebulizer (DIHEN). The best MgII 280.270 nm/MgI 285.213 nm ratio (6.6) measured with Ar ICP atomic emission spectrometry for the DIHEN (RF power = 1500 W; nebulizer gas flow rate = 0.12 L min(-1)) was less than the ratio (8.2) acquired on the same instrument for conventional nebulization (1500 W and 0.6 L min(-1)). Addition of small amounts of O2 or He (5%) to the outer gas flow improved excitation conditions in the ICP, that is, a more robust condition (a MgII/MgI ratio of up to 8.9) could be obtained by using the DIHEN with Ar-O2 and Ar-He mixed-gas plasmas, thereby minimizing some potential spectroscopic and matrix interferences, in comparison to Ar ICPAES.     

应用ICP消解氟里昂的优越性及其处理效率的初步研究

讨论了应用高频电感耦合等离子体(ICP)消解氟里昂类废弃物的可行性及与国际先进技术的比较;应用低功率ICP系统进行氟里昂12的模拟消解,用GC-ECD方法对尾气中的残余成分和浓度进行分析,证明该系统对氟里昂12的处理效率高于99.9%,可以发展成为未来环保废物处理领域的一项新技术。     

Characterization and screening of metals,metalloids and biomarkers in crude oil by ICP–MS/OES,and GC–MS techniques after digestion by microwave‐induced combustion

A method for digestion of light and medium Iraqi crude oils (Basrah and Khanaken oils) using microwave‐induced combustion (MIC) in closed vessels is described for the determination of Hg, Au, Cu, Al, Ca, Co, K, Mg, Si and Sr by inductively coupled plasma optical emission spectrometry (ICP–OES) and Mo, Ti, Mn, Li, Se^?1, Rb, Ag, Ba, Pb, As, Cd, Cr, Fe, Ni, V and Zn by inductively coupled plasma mass spectrometry (ICP–MS). Upon using MIC it was possible to obtain lower limits of detection by ICP–MS and also by ICP–OES compared with those obtained by microwave‐assisted digestion. The MIC was the best choice with regard to the possibility of using dilute nitric acid as an absorbing solution, which is important to minimize the interference encountered by ICP–MS and ICP–OES.The physicochemical parameters and some contaminants of crude oil samples were analyzed to classify and assess the quality of the crude oils. This study determines the viability of the use of Fourier transform infrared spectroscopy as an alternativee to traditional petroleum geochemical methods for crude oil characterization. The infrared fingerprints agree with the results obtained from GC–MS analysis.     

On the operation of inductively coupled plasmas as a function of pressure

The effect of pressure on the operating conditions within a 27-MHz inductively coupled plasma is investigated. The results show a direct relationship between torch pressure and the excitation temperature of an analyte species introduced into the plasma. The excitation temperature of the plasma support gas is shown to increase with torch pressure. A shift towards local thermal equilibrium is also observed with increasing pressure. The possibility of using alternate plasma support gases such as He is also investigated.     

Thermodynamic considerations and optical emission diagnostics of a N2/O2 mixture in an inductively coupled air plasma

Composition, monatomic spectral line intensities (Cu, O, N) and enthalpy are calculated for thermal and non-thermal equilibrium conditions in a plasma composed of three plasma gas mixtures of N₂, O₂ and an aerosol of copper sulfate in water. With these mixtures, the excitation and rotational temperatures are measured in an inductively coupled plasma (ICP) torch using monatomic Cu spectral lines and CuO molecular spectra, respectively. It is shown that with the enthalpy it is possible to deduce the electronic translation temperature for other mixtures and that this ICP torch allows us to check the diatomic simulated spectra.     

Using of Fractional Separation for the Analysis of MoO<Subscript>3</Subscript> by Atomic Emission Spectrometry with Inductively Coupled Plasma and Electrothermal Vaporization

The introduction of various forms of molybdenum into an inductively coupled plasma was studied in the vaporization of solutions from a graphite tube. A temperature program is selected that enables the separated vaporization of analytes and molybdenum (matrix) for atomic emission spectrometry with inductively coupled plasma and electrothermal vapoization (ETV–ICP–AES) analysis. The limits of detection for analytes in the ETV–ICP–AES analysis of molybdenum trioxide are evaluated using the fractional separation of analytes and the matrix.     

On the charge transfer in an inductively coupled argon plasma

Absolute population densities for several excited states of magnesium are obtained for several locations in an inductively coupled plasma (ICP). They were used to construct Boltzmann-Saha plots for these positions and show that magnesium is close-to-LTE. The deviations from LTE are mainly limited to the levels sensitive to charge exchange with argon ions. These measured deviations can be explained by a simple model which shows that, although charge transfer is a dominant excitation and ionization mechanism in an ICP, the associated LTE deviations are limited in magnitude.     

Abweichungen vom lokalen thermischen Gleichgewicht im axialen Kanal eines induktiv gekoppelten Argon-Plasmas

Summary Measurement of the excited state level population of a thermometric species like FeI injected into the axial channel of an inductively coupled plasma (ICP) is a powerful method to describe the plasma, even when the level population distribution in case of deviations from local thermal equilibrium (LTE) does not define a uniform plasma temperature.The injection of the thermometric species as ferrocene vapour allows to study the specific influence of operating conditions and normal sample components such as water on the plasma conditions by adding independently the different components.It is shown that deviations from LTE-state decrease with increasing generator power and decreasing carrier gas-flow rate and reach an axial minimum in the normal analytical zone (NAZ). Although differences of more than 1000 K between excitation temperature of low lying FeI-levels and levels close to the ionization-limit have been observed, deviation of the levels population density from an LTE-distribution is smaller than a factor of 5 under reasonable analytical conditions. Under such conditions the LTE-concept seems to be a useful first approximation to describe the thermodynamics of the ICP and to predict trends.

---

---

Herrn Prof. Dr. Reinhard Nast zum 75. Geburtstag gewidmet     

Analytical atomic spectroscopy using ion trap devices

Investigations using ion trap devices for analytical atomic spectroscopy purposes have focused on the use of an inductively coupled plasma (ICP) ion source with ion trap mass spectrometric (ITMS) detection. Initial studies were conducted with an instrument assembled by simply appending an ion trap as the detector to a fairly conventional ICP/MS instrument, i.e. leaving an intermediate linear quadrupole between the plasma source and the ion trap. The principal advantages found with this system include the destruction of nearly all problematic and typical ICP/MS polyatomic ions (e.g., ArH(+), ArO(+), ArCl(+), Ar(2)(+), etc) and a dramatic reduction of the primary plasma source ion, Ar(+). These results prompted the development of a second-generation plasma source ion trap instrument in which direct coupling of the ICP and ion trap has been effected (i.e. no intermediate linear quadrupole); the same performance benefits have been largely preserved. Initial operation of this instrument is described, characterized, and compared to the originally described ICP/ITMS and conventional ICP/MS systems. In addition, experiments aimed at improving ICP/ITMS sensitivity and selectivity using broadband resonance excitation techniques are described. Finally, the potential for laser optical detection of trapped ions for analytical purposes is speculated upon.     

Use of LIBS for rapid characterization of parchment

Parchment from different sources has been analyzed by laser-induced breakdown spectroscopy (LIBS) for determination of Ca, Na, K, Mg, Fe, Cu, and Mn. The LIBS results were compared with results from inductively coupled plasma spectroscopy (ICP) and good correlation was obtained. Rapid distinction between modern and historical samples was achieved by discriminant analysis of the LIBS data. Animal type recognition was also possible on the basis of Mg/Cu emission peak ratio and Mg depth profiling.     

A status report on helium inductively coupled plasma mass spectrometry

The current status of helium inductively coupled plasma – mass spectrometry (He ICPMS) is examined, its potentials and limitations are reviewed, and a summary of fundamental properties of atmospheric pressure He ICP discharges is presented. Also included are results of He ICPMS studies with a new helium plasma torch (18 mm i.d.) operated at four sets of operating conditions. Under the cold plasma condition (600 W forward power), no secondary discharge is observed and ion kinetic energies ranging from 2.0 eV to 9.5 eV for 6 elements (mass range: 39–208) are measured. At higher power levels, the secondary discharge still is strong. In general, detection limits for certain elements are improved by 1–3 orders of magnitude compared to previous data acquired in 1993 with a 13-mm He ICP torch. Elements such as K, Fe, Cr, Mn, Ni, and Co that suffer from spectral interferences in Ar ICPMS can be detected at pg/mL-levels with an analogue detector and a prototype ICPMS instrument having no photon stops or obstacles present in the ion trajectory path.     

Laser ablation solid sampling: vertical spatial emission intensity profiles in inductively coupled plasma

Spectral emission intensity in the inductively coupled plasma (ICP) was measured versus height above the load coil during laser ablation solid-sample introduction. The laser-beam pulse width, power density, and wavelength, and the sample composition are know to effect the particle size distribution of the ablated mass. Ceramic and metal samples were ablated using nanosecond and picosecond pulses, and provided similar emission intensity profiles for common elements, indicating that changes in the particle size distribution are not manifested in the vertical spatial emission profile. The gas environment in the ablation chamber also influences the particle size distribution as well as the ablation interaction. Gas composition will influence the spatial emission intensity profile because of changes in the excitation characteristics of the ICP. A preliminary study using noble gases in the ablation interaction was conducted by keeping the spatial profile constant, maintaining a constant total gas composition to the ICP.     

高纯氧化钇的感耦等离子体发射光谱分析及基体效应的研究

以高纯氧化钇中稀土杂质的ICP-AES测定为例, 研究了基体对分析元素谱线强度的影响及基体效应与工作条件的关系, 指出基体效应除主要来自分析物进样效率的降低外, 大量基体进入ICP降低了激发温度并对分析物的电离产生抑制作用, 提出用Se内标法代替通常的基体匹配法来补偿基体效应。进行了折衷条件选择及联样量确定等研究。实样分析表明, 内标法和基体匹配法所得结果一致, 加入回收率为87-120%, 精度也符合分析要求。