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A quick and sensitive method has been developed and validated for the determination of tungsten in bulk drug substance and intermediates using either Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) or Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Sample preparation is by direct dissolution with a 80:20 (v/v) concentrated nitric acid:deionized water mixture and avoids labor intensive and potentially hazardous digestion techniques. Excellent agreement was found between ICP-AES and ICP-MS results and between Merck results and Microwave Induced Plasma Mass Spectrometry (MIP-MS) results provided by an independent raw material vendor.
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PMID:Determination of tungsten in bulk drug substance and intermediates by ICP-AES and ICP-MS. 1069 60

An improved speciation technique is presented for metal(loid)organic compounds, enabling identification and quantification of species from twelve elements: germanium, arsenic, selenium, molybdenum, tin, antimony, tellurium, iodine, tungsten, mercury, lead and bismuth. At this time it is possible to identify 29 species with boiling points between -88.5 degrees C and 250 C in gaseous, liquid and solid samples in a few minutes. This study shows as an example results from measurements of soil samples from municipal waste deposits. The HG/LT-GC/ICP-MS-(hydride generation/low temperature-gas chromatography/inductively coupled plasma-mass spectrometry) apparatus contains a home-built gas chromatograph that enables satisfactory separation of various species with a boiling point difference of > or = 14 degrees C. The absolute detection limits for the elements mentioned above were below 0.7 pg.
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PMID:A new HG/LT-GC/ICP-MS multi-element speciation technique for real samples in different matrices. 1122 Aug 34

Inorganic bismuth(III) was converted to a methylbismuth species, possibly trimethylbismuth, by a thermochemical reaction with methyllithium. It instantly vaporized and was then introduced into the ICP ion source to detect the 209Bi signal. Utilizing an exchangeable small sample cuvette placed on the tungsten boat furnace for the reaction was very favorable from the viewpoints of easy handling, no memory effect, and maintenance of furnace conditions. In this manner, the analyte was vaporized at quite a low temperature (150 degrees C). The detection limit (3sigma) was 0.13 pg of bismuth and the precision in relative standard deviation for 5.0 pg of bismuth was determined to be 3.8% (n = 7).
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PMID:Generation of a methylbismuth species and its electrothermal vaporization for the determination of bismuth by inductively coupled plasma mass spectrometry. 1122 78

The newly conceived electrothermal vaporization (ETV) system using a tungsten boat furnace (TBF) sample cuvette was designed for the direct analysis of solid samples with detection by inductively coupled plasma mass spectrometry (ICP-MS). Into this small sample cuvette, a solid mixture of the biological samples and diammonium hydrogenphosphate powder as a fusion flux was placed and situated on a TBF. Tetramethylammonium hydroxide solution was added to the mixture. After the on-furnace digestion had been completed, the analyte in the cuvette was vaporized and introduced into the ICP mass spectrometer. The solid samples were analyzed by using a calibration curve prepared from the aqueous standard solutions. The detection limit was estimated to be 5.1 pg of lead, which corresponds to 10.2 ng g(-1) of lead in solid samples when a prepared sample amount of 1.0 mg was applied. The relative standard deviation for 8 replicate measurements obtained with 100 pg of lead was calculated to be 6.5%. The analytical results for various biological samples are described.
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PMID:Direct determination of lead in biological samples by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) after furnace-fusion in the sample cuvette-tungsten boat furnace. 1122 63

A new alternative approach for the determination of molybdenum in steel is proposed, using adsorptive stripping voltammetry (AdSV). The determinations are performed in a homogeneous ternary solvent system (HTSS) composed of N,N-dimethylformamide, ethanol and water, with alpha-benzoinoxime (alpha BO) as the complexing agent and a sodium acetate-acetic acid buffer as the support electrolyte. The HTSS composition was optimized by mixture design modelling. The AdSV measurements were performed in the differential pulse mode using an accumulation potential of -1050 mV. Under these optimized experimental conditions, the Mo(VI)-alpha BO reduction current peak potential is observed at potentials near -1250 mV, much lower than those usually reported, and the calibration plot follows the polynomial equation I = 0.359 + 0.265 [CMo(VI)] - 0.015 [CMo(IV)]2 (r2 = 0.997), for Mo concentrations up to 10.0 micrograms L-1. There is a linear range in this calibration plot for Mo(VI) concentrations up to 0.20 microgram L-1, defined by the equation I = 0.353 + 0.385 [CMo(VI)] (r2 = 0.980). In both cases, I is the absolute value for the current in microA and CMo(VI) is the concentration of Mo in microgram L-1. The detection limit for this linear concentration range was estimated as 20 pg L-1. A RSD of 0.43% is associated with the signals at a Mo(VI) level of 0.72 microgram L-1. From the common method-interfering species tested, only iron at Fe/Mo(VI) ratios above 500 and vanadium and tungsten at M/Mo(VI) ratios above 100 appear to affect the analytical response significantly. Phosphorous may also reduce the analytical signal at P/Mo(VI) ratios above 100, due to the formation of the competitive P-Mo complex. The suggested routine procedure was tested by analyzing four stainless steel samples and the results compared well with the ICP-AES measurements. The higher sensitivity of this method permits direct determination of Mo(VI) in steels, eliminating the need of analyte concentration or separation steps in the sample processing procedure.
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PMID:Determination of molybdenum in steel by adsorptive stripping voltammetry in a homogeneous ternary solvent system. 1144 58

Evidence for the occurrence of Ni(CO)4 in addition to Mo(CO)6 and W(CO)6 in fermentation gases from a municipal sewage treatment plant is presented for the first time. The gases were sampled at the top of the sewage sludge digester using Tedlar bags, and were analysed using cryotrapping followed by gas chromatography coupled with inductively coupled mass spectrometry (GC-ICP-MS). The use of an ICP-MS as an element-specific detector gives sufficiently low detection limits for metals and was coupled to a packed column gas chromatograph. This method provides information about the speciation of volatile transition metals in contrast to previously used methods for the determination of Ni(CO)4 in gas samples. The element-specific detection of three different isotopes (m/z 58, 60, 62) and the correspondence of the samples' retention times with those of the standard provided convincing evidence that Ni(CO)4 is present in the fermentation gas. The concentrations found were in the sub-ppb level, which is at least one order of magnitude lower than the threshold level of 1 ppb (v/v). In addition, Mo(CO)6 and W(CO)6 were also measured in the sub-ppb range in contrast to the absence of Fe(CO)5. The stabilities of Ni(CO)4, Fe(CO)5, and Mo(CO)6 were tested in a carbon monoxide atmosphere. In the presence of distilled water, the following order of stability was found after 11 weeks: Fe(CO)5 < Ni(CO)4 < Mo(CO)6. In the presence of an aqueous solution containing nickel, molybdenum, tungsten and iron, however, only Fe(CO)5 was significantly decomposed (< 0.3% recovery); Ni(CO)4 and Mo(CO)6 were stable after 11 weeks. No W(CO)6 was formed. The low stability of Fe(CO)5 in the presence of water could be the reason why no volatile iron compound was found in sewage gas. This study showed that GC-ICP-MS can be employed to identify species-specific traces of metal carbonyls in process gases such as sewage gas.
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PMID:Determination of Ni(CO)4, Fe(CO)5, Mo(CO)6, and W(CO)6 in sewage gas by using cryotrapping gas chromatography inductively coupled plasma mass spectrometry. 1152 76

A combined method of electrothermal vaporization and low-pressure helium ICP-MS was developed for the determination of traces of arsenic in chloride solutions, because serious spectral interference occurred in conventional argon ICP-MS. On a tungsten filament was placed 5 microl of a sample and heated electrothermally to remove the solvent. The resulting residue on the filament was covered with a vaporization chamber, and after reducing the pressure to ca. 5 Torr, it was rapidly heated by discharging a high-capacity condenser (0.22 F). The vapor of arsenic was transferred to a helium plasma with a stream of carrier gas for the determination. The background was not observed at m/z of 75, which allowed the determination of arsenic at ng/ml levels in chloride solutions. Sodium chloride significantly enhanced the intensity of the arsenic signal, whereas other chlorides, including KCl, MgCl2, CaCl2 and NH4Cl, suppressed the analytical signals. This enhancement due to sodium ions seems to be a peculiar phenomenon to the helium ICP. The proposed method can be applied to direct determinations of as low as 0.9 ng/ml of arsenic in seawater.
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PMID:Electrothermal vaporization on a tungsten filament for the determination of arsenic in chloride solutions by low-pressure helium ICP-MS. 1199 58

In this work, tungsten coil (W-Coil) devices are used as atomizers for electrothermal atomization atomic absorption spectrometry (ETAAS), electrothermal atomization laser excited atomic fluorescence spectrometry (ETA-LEAFS), and electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES). For most cases in ETAAS and ETA-LEAFS, limits of detection (LODs) using the W-Coil are within a factor of ten of those observed with commercial graphite furnace systems. LOD for Cd by W-Coil AAS is 10 pg, while LODs for As, Se, Cr, Sb and Pb by W-Coil LEAFS are 950, 320, 1400, 330, and 160 fg, respectively. The compact W-Coil device makes it an ideal atomizer for portable atomic spectrometry instrumentation, especially when coupled with a miniature charge coupled device spectrometer. Alternatively, the atomizer can be used as an inexpensive, modular add-on to an existing commercial ICP-AES system; and the thermal separation of Pb with interference elements Al, Mn, and Fe is demonstrated.
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PMID:Tungsten coil devices in atomic spectrometry: absorption, fluorescence, and emission. 1199 59

The potential of the laser-induced argon spark atomizer (LINA-Spark atomizer) coupled with ICP-AES as a convenient device for direct analysis of WC/Co powdered precursors of sintered hardmetals was studied. The samples were presented for the ablation as pressed pellets prepared by mixing with powdered silver binder containing GeO2 as internal standard. The pellets were ablated with the aid of a Q-switched Nd:YAG laser (1064 nm) focused 16 mm behind the target surface with a resulting estimated power density of 5 GW cm(-2). Laser ablation ICP-AES signals were studied as a function of ablation time, and the duration of time prior to measurement (pre-ablation time) which was necessary to obtain reliable results was about 40 s. Linear calibration plots were obtained up to 10% (m/m) Ti, 9% Ta and 3.5% Nb both without internal standardization and by using germanium as an added internal standard or tungsten as a contained internal standard. The relative uncertainty at the centroid of the calibration line was in the range from +/- 6% to +/- 11% for Nb, Ta and Ti both with and without internal standardisation by Ge. A higher spread of points about the regression was observed for cobalt for which the relative uncertainty at the centroid was in the range from +/- 9% to +/- 14%. Repeatability of results was improved by the use of both Ge and W internal standards. The lowest determinable quantities calculated for calibration plots were 0.060% Co, 0.010% Nb, 0.16% Ta and 0.030% Ti with internal standardization by Ge. The LA-ICP-AES analyses of real samples led to good agreement with the results obtained by solution-based ICP determination with a relative bias not exceeding 10%. The elimination of the dissolution procedure of powdered tungsten (Nb, Ta, Ti) carbide is the principal advantage of the developed LA-ICP-AES method.
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PMID:Direct solid analysis of powdered tungsten carbide hardmetal precursors by laser-induced argon spark ablation with inductively coupled plasma atomic emission spectrometry. 1456 41

A direct determination of Al, As, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Sn, Ti and V in tungsten products with ICP-AES is presented. The influence of tungsten matrix is studied. Based on the selected optimum operating parameters, the feasibility of the proposed method is evaluated by analyzing three WO3 National References. The results are satisfactory.
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PMID:[Direct determination of trace elements in tungsten products with ICP-AES]. 1582 70


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