Determination of tungsten by direct current plasma atomic emission spectrometry

The determination of tungsten in steels and alloys with the three-electrode direct current plasma (DCP) “spectrajet” was investigated. The relative intensities of 17 spectral lines of tungsten and several possible interfering lines of its concomitants are listed. WI 400.875 nm is normally best suited, because the background produced by iron and acid is low and easily compensated for by using a blank solution. The limit of detection c_l in steels is 2 × 10^?3% W for 10 $\text{mg}\text{ml}$ of sample. The line W I 407.436 nm is preferred in the presence of much titanium. For the purpose considered the DCP provides about the same power of detection as the more expensive inductively coupled plasma (ICP), but its observation zone is less well buffered against influences from the matrix.     

Statistical mechanics of Ar2+ in an inductively coupled plasma

In the mass spectrum of an argon inductively coupled plasma (ICP), there is a peak due to the presence of the argon dimer ion, Ar₂⁺. Using elementary statistical mechanics, an attempt is made to elucidate the mechanism responsible for this ion's presence in the ICP, The assumption of local thermodynamic equilibrium (LTE) in the ICP leads to three possible mechanisms that could be responsible for the presence of the argon dimer ion, however, the results of the calculations show that only one of the mechanisms agrees with experiment. The experimental measurements of the number density ratio of Ar₂⁺ to Ar⁺, against which the theoretical values are compared, were taken using inductively coupled plasma mass spectrometry (ICP-MS),     

BeF-Emissionsbanden im induktiv gekoppelten plasma

In this study we try to detect metal fluoride bands in the inductively coupled plasma. BeF¹ provided the most intense spectra with a head at 300.99 nm. Maximum intensity of BeF¹ was found under the following conditions: high carrier gas flow, low power level and low observation height above the load coil. The detection limit of fluoride by means of molecular emission was 400 mg l^?1.     

Observation of spectral line profiles emitted by an inductively coupled plasma—I.: On the wavelength shift of spectral lines

Profiles of 16 spectral lines stemming from 8 elements (Ar, Na, Cu, Sr, Cd, Ba, Mg and Li) emitted by an inductively coupled plasma (ICP) have been observed and measured with a pressure-scanning Fabry-Perot interferometer. In the process of profile observations, we have found wavelength shifts of spectral lines in an ICP and for the first time studied this phenomenon quantitatively and systematically in a spectrochemical source. The profiles of spectral lines emitted by the ICP have been compared with those emitted by hollow cathode lamps. The magnitude of the wavelength shift to the red or the blue varied more or less with the plasma conditions, observation position and the concentration of a concomitant, cesium. In the present work the observed line profiles were not deconvoluted for the apparatus profiles. Typically the order of magnitude of the wavelength shift measured for spectral lines that show large shifts at an observation height of about 4 mm in an “analytical” ICP is n × 10^?3 nm, where n is about 4 for Ar I 427.2 nm and about 1 for Cu I 521.8 nm and Sr II 430.5 nm. With regard to the wavelength shift, several trends and/or regularities were found. The Stark effect is considered as the main cause of the phenomena.     

Determination of calcium in water by flow injection analysis — inductively coupled plasma (FIA-ICP) emission spectrometry

Summary Using an 11 ml centrifugal type spray chamber, a rapid sample introduction rate of 320 injections per hour may be achieved when interfacing flow injection analysis and inductively coupled plasma emission spectrometric techniques. Calcium was determined in water samples with a relative standard deviation of better than 3.5% over the analytical range of 10 to 200 mg · l^–1 Ca. Mean recovery was 97%.

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Calciumbestimmung im Wasser mit dem Flow-injection-Prinzip kombiniert mit der Induktions-gekoppelten Plasma-Emissions-Spektrometrie (FIA-ICP)

     

Comparing the capability of collision/reaction cell quadrupole and sector field inductively coupled plasma mass spectrometers for interference removal from 90Sr, 137Cs,and 226Ra

Here we report a quantitative comparison of sector field inductively coupled plasma mass spectrometry (ICP-SFMS) and collision/reaction cell inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) for the detection of ⁹⁰Sr, ¹³⁷Cs, and ²²⁶Ra at ultra-trace levels. We observed that the identification and quantification of radioisotopes by ICP-MS were hampered by spectral (both isobaric and polyatomic ions) and non-spectral (matrix effect) interferences. ICP-QMS has been used to eliminate the isobaric ⁹⁰Sr/⁹⁰Zr interference through the addition of O₂ into the collision cell as a reactant gas. Zr⁺ ions were subsequently converted into ZrO⁺, whereas Sr⁺ ions were not reactive. In addition, the isobaric interference of ¹³⁷Ba on ¹³⁷Cs was eliminated by the addition of N₂O gas in the cell, which led to the formation of BaO⁺ and BaOH⁺ products, whereas Cs⁺ remained unreactive. Furthermore, He and H₂ were used in the collision/reaction cell to eliminate polyatomic ions formed at m/z 226. A comparison of the results obtained by ICP-SFMS after a chemical separation of Sr from Zr and Cs from Ba was performed. Finally, to validate the developed analytical procedures, measurements of the same samples were performed by γ-ray spectroscopy.     

Quantification of water and plasma diagnosis for electrothermal vaporization–inductively coupled plasma–mass spectrometry: the use of argon and argide polyatomics as probing species

The water content of the carrier flow originating from an electrothermal vaporization unit (ETV) attached to an inductively coupled plasma mass spectrometer was monitored by following the argon hydride ion (ArH⁺) at m/z=37. The goal was to measure the water expelled by the ETV at sample vaporization and evaluate the influence of this parameter on the ion-generation efficiency. Linear responses from the argon hydride were obtained when the water loading in the plasma injector flow was increased from 0 to 3.3 mg/min. Other argides and water-derived species (Ar⁺, Ar⁺₂ and O⁺₂) were also monitored simultaneously and the effects from operating parameters have been calculated for each species. The magnitude of these effects can eventually be used as diagnosis tools. It was also found that signals for zinc, copper, lead, antimony and arsenic were greatly influenced by slight variations in water loading at low water levels. These signal fluctuations are greatly attenuated and transients' shapes restored by convoluting each element transient with the ArH⁺ or Ar⁺₂ curves that were recorded simultaneously. Envisioned applications that would benefit from a water-enhanced signal include spray electrothermal vaporization, direct sample insertion and laser ablation for inductively coupled plasma–mass spectrometry. The argon dimer Ar⁺₂ seems more appropriate for making the correction since it provides a direct insight on the plasma temperature and provides a robust signal.     

An echelle polychromator for inductively coupled plasma optical emission spectroscopy with vacuum ultraviolet wavelength coverage and charge injection device detection

The development and evaluation of a simultaneous inductively coupled plasma optical emission spectrometer with vacuum ultraviolet (VUV) wavelength coverage and charge injection device (CID) detection are described. The spectrometer is an echelle polychromator with a magnesium fluoride prism as a cross-disperser. A thin coating of Lumogen, used as a wavelength conversion phosphor, is applied to the surface of the CID detector. The Lumogen coating increases sensitivity in the VUV region dramatically. Wavelengths between 130 and 800 nm can be measured by this spectrometer. A measured spectral bandwidth of 0.006 nm at 134.724 nm is achieved. The analytical performance in radial viewing mode is evaluated. The 3σ detection limit measured for Cl at 134.724 nm in aqueous solution is 100 ng ml⁻¹.     

Development of cadmium/silver/palladium separation by ion chromatography with quadrupole inductively coupled plasma mass spectrometry detection for off-line cadmium isotopic measurements

A separation method was investigated to perform off-line cadmium isotopic measurements on a ¹⁰⁹Ag transmutation target. Ion chromatography (IC) with Q ICPMS detection (quadrupole inductively coupled plasma mass spectrometry detection) was chosen to separate cadmium from the isobarically interfering elements, silver and palladium, present in the sample. The optimization of chromatographic conditions was particularly studied. Several anion and cation columns (Dionex AG11^®, CS10^® and CS12^®) were compared with different mobile phases (HNO₃, HCl). The separation procedure was achieved with a carboxylate-functionalized cation exchange CS12 column using 0.5 M HNO₃ as eluent. The developed technique yielded satisfactory results in terms of separation factors (greater than 5) and provides an efficient solution to obtain rapidly purified cadmium fractions (decontamination factors higher 100,000 for silver and palladium) which can directly be analyzed by multi collection inductively coupled plasma mass spectrometry (MC ICPMS). By applying the proposed procedure, accurate and precise cadmium isotope ratios were determined for the irradiated ¹⁰⁹Ag transmutation target.     

Determination of Hg in seawater by inductively coupled plasma mass spectrometry after on-line pre-concentration

A method for the determination of Hg in seawater by inductively coupled plasma mass spectrometry, after an on-line separation and pre-concentration, is described. The matrix separation was accomplished by retention of the Hg complex with the ammonium salt of O,O-diethyl dithiophosphoric acid on C₁₈ immobilized on silica in a micro-column. Before pre-concentration, the seawater sample was acidified with HNO₃ to 0.14 mol l⁻¹. Methanol was used as the eluent, which was introduced into the conventional pneumatic nebulizer of the instrument. External calibration with aqueous analytical solutions, submitted to the same procedure, was used. An enhancement factor of 16 was obtained, and the limit of detection was 5 ng l⁻¹. The sample consumption was 2.3 ml per determination, and the sampling frequency was 21 h⁻¹. The accuracy was tested by comparison with vapor generation inductively coupled plasma mass spectrometry. The agreement between the Hg concentrations measured by the two methods in the seawater samples was good.     

An assessment of a microwave-induced plasma generated in argon with a cylindrical TM010 cavity as an excitation source for emission spectrometric analysis of solutions

A cross-flow pneumatic nebulizer with spray chamber was directly coupled to a microwave-induced plasma (MIP) generated with a cylindrical TMO₀₁₀ cavity in argon flowing through an alumina capillary. The detection limits of 15 elements were determined with 23 spectral lines and the interference effect of KCl on these spectral lines was measured. The results were compared with those reported in the literature for MIP systems based on conventional or newly designed cavities, and incorporating desolvation facilities. A comparison was also made with an inductively coupled plasma (ICP) and a capacitively coupled microwave plasma (CMP) for which the reported results were obtained under spectrometric conditions that closely matched those used in the present work and for which the rate of sample injection into the plasma was approximately the same as that used here.     

Speciation of chromium in waste water using ion chromatography inductively coupled plasma mass spectrometry

Ion chromatography (IC) coupled with inductively coupled plasma mass spectrometry (ICP-MS) was systematically investigated for determining the speciation of chromium in environmental samples. Firstly, the stability of complexes formed by Cr(III) with various aminopolycarboxylic acids was studied by electrospray ionization mass spectrometry (ESI-MS). The results showed that [Cr(EDTA)]⁻ was stable in solution. Secondly, various mobile phases were examined to separate Cl⁻ from chromium species by IC to avoid Cl⁻ interference. The separation of [Cr(EDTA)]⁻ and Cr(VI) was achieved on a new anion-exchange column (G3154A/102) using a mobile phase containing 20 mM NH₄NO₃ and 10 mM NH₄H₂PO₄ at pH 7.0 without Cl⁻ interference. Detection limits for chromium species were below 0.2 μg/L with a direct injection of sample and without prior removal of interferences from the matrix. Finally, the proposed method was used for the determination of chromium species in contaminated waters.     

Determination of hexavalent chromium in traditional Chinese medicines by high‐performance liquid chromatography with inductively coupled plasma mass spectrometry

An analytical method that combined high‐performance liquid chromatography with inductively coupled plasma mass spectrometry has been developed for the determination of hexavalent chromium in traditional Chinese medicines. Hexavalent chromium was extracted using the alkaline solution. The parameters such as the concentration of alkaline and the extraction temperature have been optimized to minimize the interconversion between trivalent chromium and hexavalent chromium. The extracted hexavalent chromium was separated on a weak anion exchange column in isocratic mode, followed by inductively coupled plasma mass spectrometry determination. To obtain a better chromatographic resolution and sensitivity, 75 mM NH₄NO₃ at pH 7 was selected as the mobile phase. The linearity of the proposed method was investigated in the range of 0.2–5.0 μg L^?1 (r² = 0.9999) for hexavalent chromium. The limits of detection and quantitation are 0.1 and 0.3 μg L^?1, respectively. The developed method was successfully applied to the determination of hexavalent chromium in Chloriti lapis and Lumbricus with satisfactory recoveries of 95.8–112.8%.     

H2 plasma development of X-ray imaged patterns on plasma-polymerized resists

An X-ray imaged pattern on a plasma-polymerized film was successfully developed by H₂ plasma etching. Plasma-polymerized MMA and 6FBMA were formed by using an inductively coupled argon flow type reactor. An X-ray imaged pattern on the film was attained through a knife-cut window of a gold plate. The X-ray was generated from a Cu target at 20 kV and main wavelength 1.54 Å. The pattern development was performed using a tubular type reactor with parallel plate electrodes. The quality of plasma-polymerized resists in an X-ray lithography was evaluated by comparing it with the conventional polymer in the dry and wet process, and the minimum dose rate for a visible pattern fabrication was measured to be 4.1 J/cm² for both resists in H₂ plasma etching development.     

In-situ vaporization and matrix removal for the determination of rare earth impurities in zirconium dioxide by electrothermal vaporization inductively coupled plasma atomic emission spectrometry

A novel method for the determination of trace rare earth impurities in ZrO₂ powder has been developed based on electrothermal vaporization inductively coupled plasma atomic emission spectrometry. A polytetrafluoroethylene slurry was used as a fluorinating reagent to convert both the matrix (Zr) and the analytes (rare earth elements) into fluorides with different volatilities at a high temperature in a graphite furnace. The more volatile ZrF₄ was removed in-situ by selective vaporization prior to the determination of the analytes, removing matrix spectral interferences. Under optimum operating conditions, the absolute detection limits of the analytes varied from 0.04 ng (Yb) to 0.50 ng (Pr) with relative standard deviations less than 5%. The recommended approach has been successfully applied to the determination of trace rare earth impurities (La, Pr, Eu, Gd, Ho and Yb) in ZrO₂ powder and the results were in good agreement with those obtained by pneumatic nebulization inductively coupled plasma atomic emission spectrometry after the separation of the matrix using a solvent extraction procedure.     

Analysis of germanium and germanium dioxide samples by mass-spectrometry and atomic emission spectroscopy

Three multielement methods: (1) inductively coupled plasma mass spectrometry (ICP-MS), (2) inductively coupled plasma atomic emission spectroscopy (ICP-AES), and (3) spark source mass spectrometry (SSMS) were used for the determination of additives in the samples of germanium and germanium oxide. The detection limits of direct SSMS and ICP-AES/ICP-MS were compared using the autoclave predissolution of germanium and germanium dioxide samples. It was shown that in the latter case, the detection limits could be significantly improved by the separation of germanium from analytes by distillation. In this case, the detection limits of such limiting elements like Th and U can reach the level n 10^?10 wt %.     

Determination of hafnium at the 10% level (relative to zirconium content) using neutron activation analysis,inductively coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectrometry

Hafnium at the very low level of 1–8 ppm (in relation to zirconium) was determined in zirconium sulfate solutions (originating from investigations of the separation of ca. 44 ppm Hf from zirconium by means of the ion exchange method) by using three independent methods: inductively coupled plasma mass spectrometry (ICP MS), neutron activation analysis (NAA) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The results of NAA and ICP MS determinations were consistent with each other across the entire investigated range (the RSD of both methods did not exceed 38%). The results of ICP-AES determination were more diverse, particularly at less than 5 ppm Hf (RSD was significantly higher: 29–253%). The ion exchange method exploiting Diphonix^® resin proved sufficient efficiency in Zr–Hf separation when the initial concentration ratio of the elements ([Zr]₀/[Hf]₀) ranged from 1200 to ca. 143,000.     

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.     

Direct determination of arsenic in fresh and saline waters by electrothermal vaporization inductively coupled plasma mass spectrometry

A method is described for the direct determination of arsenic in fresh and saline waters by electrothermal vaporization inductively coupled plasma mass spectrometry. Arsenic could be determined directly in waters containing up to 10 000 μg ml⁻¹ NaCl without interference from the formation of ⁷⁵ArCl⁺. For non-saline waters, arsenic was determined directly with the addition to both aqueous calibration standards and samples of 0.1 μg each of Pd and Mg to act as physical carriers. For the analysis of highly saline waters, the use of Pd and Mg chemical modifier served to thermally stabilize arsenic up to a temperature of 1000°C, while the separate addition of 8 mg of ammonium nitrate was used to remove chloride from the sample. This eliminated serious spectral interference on ⁷⁵As⁺ from ⁷⁵ArCl⁺. Although the ArCl⁺ spectral interference was completely eliminated, residual Na co-volatilized with As caused signal suppression, requiring the use of the method of standard additions for calibration. An absolute limit of detection limit for As of 0.069 pg was obtained corresponding to 6.9 pg ml⁻¹ in a 10 μl sample.     

Combination of cool plasma and collision-reaction interface for correction of polyatomic interferences on copper signals in inductively coupled plasma quadrupole mass spectrometry

Inductively coupled plasma mass spectrometry (ICP-MS) is an important instrumental technique for elemental analysis. However, some elements suffer from spectral interferences caused by ions derived from argon plasma gas and matrix components. The determination of copper isotopes is affected by ⁴⁰Ar²³Na⁺ and ⁴⁰Ar²⁵Mg⁺. The performance of an ICP-MS with a collision reaction interface (CRI) and cool plasma conditions for correction of spectral interferences was evaluated here. The efficiency of the CRI was studied introducing H₂ or He through sampler and skimmer cones. Gas introduction through the sampler cone was ineffective. Complete elimination of spectral interferences was reached when introducing 60 or 80 mL min⁻¹ of H₂ in the skimmer cone, but sensitivity losses were as large as 99%. Further, the effect of interferences was checked when the argon plasma was operated under cool plasma conditions. The effects of the applied radiofrequency (0.6, 0.8, 0.9, and 1.0 kW), sampling depth (5.5, 8.5 and 11.5 mm), and dwell time (25 and 50 ms) were studied considering interference reduction and sensitivities. Best conditions were reached at 0.8 kW. Subsequently, both CRI and cool plasma conditions were combined to evaluate their performance on reduction of polyatomic Na and Mg argide interferences. Spectral interferences were eliminated using a CRI with 20 mL min⁻¹ H₂ introduced through the skimmer cone, cool plasma conditions at 0.8 kW and sampling depth of 8.5 mm. This work demonstrated the feasibility of combining CRI and cool plasma for circumventing some spectral interferences on Cu determination by ICP-QMS.