Determination of trace impurities in electronic grade quartz: Comparison of inductively coupled plasma mass spectroscopy with other analytical techniques

An analytical procedure for the determination of uranium and thorium in the sub-ng/g range as well as of other trace elements in the ng/g to g/g range in high purity quartz samples is described. The results obtained by inductively coupled plasma mass spectroscopy (ICP-MS) are compared to those obtained by other analytical techniques (instrumental neutron activation analysis, INAA; flame atomic absorption spectrometry, AAS; Zeeman graphite furnace atomic absorption spectrometry, ZGFAAS; total reflection X-ray fluorescence analysis, TRFA; direct current arc optical emission spectrometry, DC-arc OES; and X-ray fluorescence analysis, XRFA). For the ICP-MS measurements, the decomposition of the samples is carried out with HF/HNO₃/H₂SO₄-mixtures. The results obtained by the different methods show reasonable agreement. For uranium and thorium, ICP-MS proves to be the most sensitive method: detection limits of about 50 pg/g can be achieved for both elements.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria     

Derivative flame atomic absorption spectrometry and its application in trace analysis

Flame atomic absorption spectrometry (FAAS) is an accepted and widely used method for the determination of trace elements in a great variety of samples. But its sensitivity doesn’t meet the demands of trace and ultra-trace analysis for some samples. The derivative signal processing technique, with a very high capability for enhancing sensitivity, was developed for FAAS. The signal models of conventional FAAS are described. The equations of derivative signals are established for FAAS, flow injection atomic absorption spectrometry (FI-FAAS) and atom trapping flame atomic absorption spectrometry (AT-FAAS). The principle and performance of the derivative atomic absorption spectrometry are evaluated. The derivative technique based on determination of variation rate of signal intensity with time (dI/dt) is different from the derivative spectrophotometry (DS) based on determination of variation rate of signal intensity with wavelength (dI/dλ). Derivative flame atomic absorption spectrometry (DFAAS) has higher sensitivity, lower detection limits and better accuracy. It has been applied to the direct determination of trace elements without preconcentration. If the derivative technique was combined with several preconcentration techniques, the sensitivity would be enhanced further for ultra-trace analysis with good linearity. The applications of DFAAS are reviewed for trace element analysis in biological, pharmaceutical, environmental and food samples.     

Determination of cobalt in sewage sludge using ultrasonic slurry sampling graphite furnace atomic absorption spectrometry

Cobalt in sludge of domestic and industrial origin, with high iron contents (> 17 g/kg), was determined by slurry sampling graphite furnace atomic absorption spectrometry (GF-AAS). Slurries prepared by ultrasonic stirring were adequately diluted to cover the variation in cobalt content in the sludge samples. The diluent was 5% HNO₃. Standard atomisation conditions for cobalt determination were used and no matrix modifier was applied. Slurry sampling GF-AAS results in the sludge were verified by analysing totally digested samples by inductively coupled plasma atomic emission spectrometry (ICP-AES) and by GF-AAS. The procedure was validated by analysing the certified reference material BCR 146 R, a sewage sludge of industrial origin. Recoveries for cobalt in the spiked slurried sludge samples ranged from 92 to 96%, with a relative standard deviation of 10%. Recoveries in the certified sludge using slurry sampling GF-AAS technique were about 103% for a cobalt content of 7.39 mg/kg.     

Suppression of interferences in the determination of lead in natural and drinking waters by graphite-furnace atomic absorption spectrometry

The problem of matrix interference encountered in the determination of lead in natural and drinking waters by graphite furnace atomic absorption spectrometry is examined by looking at the individual effects of various constituent salts (NaCl, KCl, MgCl₂ and CaCl₂, Na₂SO₄, KH₂PO₄ and Mg(NO₃)₂), of which MgCl₂ and Na₂SO₄ interfered most severely. The use of the L'vov platform decreased the sulphate interference, but was not successful in removing the other interferences. The mixture of 0.05% (w/v) lanthanum (as LaCl₃) and 1% (v/v) nitric acid previously proposed for wall atomisation was found to be effective in controlling the interferences. Nitric acid alone removed almost completely the effects of MgCl₂ and CaCl₂, but had little effect on the interference of sulphate, which required the addition of lanthanum for suppression. The removal of interferences in real water samples by the lanthanum/nitric acid mixture is demonstrated by comparison of results obtained by this approach with those obtained by atomic fluorescence spectrometry and by flame atomic absorption spectrometry after preconcentration by evaporation.     

Determination of Cd, Co, Cu, Mn, Ni, Pb, and Zn by Inductively Coupled Plasma Mass Spectroscopy or Flame Atomic Absorption Spectrometry after On-line Preconcentration and Solvent Extraction by Flow Injection System

The concentrations of Cd, Co, Cu, Mn, Ni, Pb, and Zn in natural and sea waters are too low to be directly determined with by flame atomic absorption spectrometry (FAAS) or graphite furnace atomic absorption spectrometry (GFAAS). Specific sample preparations are requested that make possible the determination of these analytes by preconcentration or extraction. These techniques are affected by severe problems of sample contamination. In this work Cd, Co, Cu, Mn, Ni, Pb, and Zn were determined by inductively coupled plasma mass spectroscopy (ICP-MS) or by atomic absorption spectrometry, in fresh and seawater samples, after on-line preconcentration and following solvent elution with a flow injection system. Bonded silica with octadecyl functional group C₁₈, packed in a microcolumn of 100-μl capacity, was used to collect diethyldithiocarbamate complexes of the heavy metals in aqueous solutions. The metals are complexed with a chelating agent, adsorbed on the C₁₈column, and eluted with methanol directly in the flow injection system. The methanolic stream can be addressed to FAAS for direct determination of Cu, Ni, and Zn, or collected in a vial for successive analysis by GFAAS. The eluted samples can be also dried in a vacuum container and restored to a little volume with concentrated HNO₃and Milli-Q water for analysis by ICP-MS or GFAAS.     

A comparative study of standards for determinations of trace wear metals in jet engine oils

The feasibility of using acid-treated metal powder standards for the determination of trace wear metals in spent jet engine oils is evaluated. The addition of 2:3:3 (v/v/v) HF—HCl—HNO₃ mixture to used lubricating oils did not cause any statistically reliable differences from results obtained with organometallic standards. Two sets of six correlation samples, one set being acid-treated, were analyzed for Cu, Cr, Mg, Fe, Mo and V by flame atomic absorption and flame atomic fluorescence spectrometry against each set of standards.     

Comparison of Pyrolysis and Microwave Acid Digestion Techniques for the Determination of Mercury in Biological and Environmental Materials

 Microwave digestion reduction-aeration and pyrolysis combined with cold vapour atomic absorption and cold vapour atomic fluorescence are compared for the determination of total mercury in several biological and environmental matrices. The biological samples were digested in a mixture of HNO₃/H₂O₂, the environmental samples in a mixture of HNO₃/HClO₄. After reduction with SnCl₂, the mercury was collected by two-stage gold amalgamation. After microwave digestion reduction-aeration, detection limits of 1.4 ng g⁻¹ and 0.6 ng g⁻¹ were obtained for cold vapour atomic absorption spectrometry (CVAAS) and cold vapour atomic fluorescence spectrometry (CVAFS), respectively, for 250 mg of environmental samples. For biological samples (500 mg) the detection limits were 0.7 ng g⁻¹ (CVAAS) and 0.4 ng g⁻¹ (CVAFS). After pyrolysis, detection limits of 3.5 ng g⁻¹ and 1.6 ng g⁻¹ for CVAAS and CVAFS, respectively, were obtained for a 10 mg sample. Pyrolysis can only be applied when the organic content of the sample is not too high. Accurate results were obtained for 8 certified reference materials of both environmental and biological origin. In addition, a real sludge sample was analysed. Author for correspondence. E-mail: richard.dams@rug.ac.be Received September 18, 2002; accepted December 3, 2002 Published online May 5, 2003     

Determination of aluminium in AlCl3 and Al2O3 modified silica catalyst supports

X-ray fluorescence spectrometry (XRF) was applied to determine aluminium in AlCl₃- and Al₂O₃-modified silica catalyst supports that were prepared by gas-solid reactions in an atomic layer epitaxy (ALE) process using aluminium chloride or aluminium chloride and water as adsorbates and silica as support. INAA and AAS were used as reference methods to determine the aluminium content of the supports. The calibration of XRF results was done by plotting the Al/Si intensity ratios against the aluminium content as determined by atomic absorption spectrometry (AAS) and verified by instrumental neutron activation analysis (INAA). Correlation factors for the calibration graphs were 0.984 for AlCl₃/SiO₂ and 0.995 for Al₂O₃/ SiO₂ samples in the aluminium content range 0–2.6 g Al per 100 g of sample. Received: 19 October 1998 / Accepted: 14 December 1998     

Determination of aluminium in AlCl3 and Al2O3 modified silica catalyst supports

X-ray fluorescence spectrometry (XRF) was applied to determine aluminium in AlCl₃- and Al₂O₃-modified silica catalyst supports that were prepared by gas-solid reactions in an atomic layer epitaxy (ALE) process using aluminium chloride or aluminium chloride and water as adsorbates and silica as support. INAA and AAS were used as reference methods to determine the aluminium content of the supports. The calibration of XRF results was done by plotting the Al/Si intensity ratios against the aluminium content as determined by atomic absorption spectrometry (AAS) and verified by instrumental neutron activation analysis (INAA). Correlation factors for the calibration graphs were 0.984 for AlCl₃/SiO₂ and 0.995 for Al₂O₃/ SiO₂ samples in the aluminium content range 0–2.6 g Al per 100 g of sample. Received: 19 October 1998 / Accepted: 14 December 1998     

Arsenic extraction in marine biological materials using pressurised liquid extraction

A pressurised liquid extraction (PLE) procedure, by using methanol/water mixture, was developed for extracting arsenical species from marine biological material (mussel and fish) and standard reference materials (CRMs). A Plackett-Burman 2⁸ × 3/64 designs (PBD) was used as a multivariate strategy for the evaluation of the effects of several variables (MeOH/H₂O solvent mixture, temperature, static time, extraction steps, pressure, mean particle size and diatomaceous earth (DE) mass/sample mass ratio) on the extracting procedure. Electrothermal atomic absorption spectrometry (ETAAS) was used to determine the total As concentration on the methanolic extracts. The accuracy of the optimised extraction procedure was verified by analysing several CRMs (GBW-08751, BCR-278R and DORM-2). The precision obtained (between 4.5 and 6.2%) was adequate. The extracted arsenic species (mainly arsenobetaine (AsB)) were analysed by high performance liquid chromatography coupled to ultraviolet cracking and hydride generation-atomic fluorescence spectrometry (HPLC-UV-HG-AFS). The analytical performances obtained were adequate for the arsenic speciation in marine biological samples; LOD between 10 and 35 ng g⁻¹. The accuracy was verified for AsB using DORM-2. Finally, the proposed method (PLE followed by HPLC-UV-HG-AFS) was applied to mussel and fish samples.     

Synthesis and Magnetic Property of Fe-B Amorphous Alloy Nanowires by Inducing DC Magnetic Field

One dimension (1D) Fe-B amorphous alloy nanowires with diameter of 50-80 nm and length of several micrometers were synthesized under weak DC (direct current) magnetic field by KBH₄ reducing in aqueous solution. The structure, composition, and morphology were characterized by X-ray diffraction (XRD), inductively coupled plasma atomic emission spectrometry (ICP-AES), and scanning electron microscope (SEM), respectively. The results revealed that the magnetic field led to the fabrication of Fe-B amorphous alloy nanowire structure. Vibrating sample magnetometer (VSM) has been used to detect the magnetic properties of the samples. The results showed that the inducing of magnetic field had obvious effect on the magnetic properties of the samples.     

Untersuchungen zur Bestimmung von Bi, Cd, Hg, Pb und Tl in hochreinem Gallium durch Graphitrohr-AAS bei Verdampfung fester Proben

Summary Traces of Bi, Cd, Hg, Pb and Tl in the lower ·g^–1 range are determined by direct electrothermal atomic absorption spectrometry in samples of about 5 mg of metallic gallium (S_r about 0.1). Electrolytically spiked samples of high-purity gallium are used for calibration. For the analysis of high-purity gallium (7–8 N) the limit of detection of Bi, Hg and Pb can be simply improved for 2–3 orders of magnitude by previous partial dissolution of larger weighed samples in acid according to [2]. The accuracy of the analytical results was verified by ICP mass spectrometry.     

Interference-free atomic spectrometric method for the determination of trace amounts of germanium by utilizing the vaporization of germanium tetrachloride

Trace amounts of germanium can be determined by atomic spectrometry by utilizing the vaporization of germanium tetrachloride at ambient temperature. Using an intermittent or continuous flow reactor, the sample solution was mixed with concentrated hydrochloric acid to form volatile germanium tetrachloride which can subsequently be determined by atomic spectrometry. The conditions for the volatilization of germanium chloride were investigated in detail and rapid method for the determination of trace amounts of germanium in real samples was proposed. A detection limit of 0.5 ng ml⁻¹ (3σ_n−1) was obtained by using atomic fluorescence spectrometric detection and the precision found was 0.8% for a germanium concentration of l00 ng ml⁻¹. Atomic emission and absorption spectrometric methods were also tested. Owing to the high selectivity of the reaction, no interference was found in the determination. The method was applied to the determination of germanium in several standard and certified reference materials; the results obtained were in good agreement with the certified values.     

Analysis of degradation processes of C/C composites and coating layers with tracer elements in an air-acetylene flame by two-dimensional atomic absorption spectrometry

This paper describes a novel measurement technique for in-situ monitoring of the degradation processes of coated C/C composites (carbon fiber-reinforced carbon composites) in combusting fields. The samples tested in this experiment were C/C composites with double coating layers of SiC and glass materials doped with Ca and/or Mg as tracer elements. These samples were exposed in an C₂H₂/air flame emitted the diatomic molecules, and the light from the Mg-Ca hollow cathode lamp passed through the flame around the sample. The spectrally and spatially resolved images of emission were observed with a spectro CCD camera developed by our group. In this work, two-dimensional atomic absorption spectrometry by using the spectro CCD camera was applied to in-situ monitor the degradation processes of each coating layer and the substrate. The results indicated that the temporal changes in the spatial distribution of atomic absorption caused by Ca and Mg atoms proved to be a good measure for in-situ monitoring of the degradation processes of coated C/C composites in a high temperature flame.     

Atomic Fluorescence Determination of Selenium Using Hydride Generation Technique

Abstract

Hydride generation followed by atomic fluorescence spectrometry, a simple and very sensitive technique, has been evaluated for selenium analysis in different environmental and biological samples. Research is focused on the interfering effects of several selected anions, cations, and acids on the selenium determination and the sample preparation procedures. Besides some transition metals such as Ni²⁺ Co²⁺ and Cu²⁺ HNO₃ acid, the digestion medium used for sample preparation, shows strong interference. In order to reduce this interfering effect, matrix match or standard addition is recommended. This technique is validated by analyzing a number of standard reference materials. Results for selenium analysis in some biological samples are also presented.     

Negative thermal ionization mass spectrometry of selenium part 4. Selenium trace determination in sediments and related samples

Summary Selenium traces have been determined in different sediments (estuarine, river, lake), sandy soil and sewage sludge with isotope dilution mass spectrometry (IDMS). Negative selenium atomic ions are formed in a double-filament thermal ion source. The use of a silica gel technique for ionization improves the mass spectrometric sensitivity by a factor of 40 compared with the technique previously applied. An enriched⁸²Se spike is used for the isotope dilution process. The samples are decomposed with a mixture of conc. HNO₃ and conc. HE After decomposition selenium is separated by the formation of SeH₂ in a hydride generation system which is normally applied for atomic absorption spectrometry. The IDMS results for three standard reference sediments agree well with the certified values. In the case of three other standard reference materials, which are not certified for selenium up to now, the IDMS analyses were able to improve the selenium data given for information or as indicative values. The precision of the IDMS method in the concentration range of 0.2–3.5 g/g lies between 0.8 % and 4.1 %. The detection limit is 6 ng/g. A comparison with several other methods shows that IDMS is one of the very few analytical methods which produces accurate selenium results even at concentration levels of 0.2 g/g and less in sediments and related samples of environmental interest.

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Negative Thermionen-Massenspektrometrie von Selen Teil 4. Selenspurenbestimmung in Sedimenten und vergleichbaren Proben

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Dedicated to Prof. Dr. G. Tblg on the occasion of his 60th birthday     

Atomic absorption spectrometric determination of trace tellurium after hydride trapping on platinum-coated tungsten coil

In this work, a sensitive and simple method for the determination of tellurium was developed by hyphenation of electrically heated quartz tube atomic absorption spectrometry and tellurium hydride trapping on platinum-coated tungsten coil. With a mixture of Ar and H₂, tellurium hydride was transported to tungsten coil for trapping at 390 °C and releasing at 1200 °C. A limit of detection (LOD, 3σ) of 0.08 ng mL^{− 1} was obtained with 1 min trapping (1.5 mL sampling volume), and enhancement factor was 28 compared to conventional hydride generation atomic absorption spectrometry. The LOD was better or at least comparable to literature levels involving on-line trapping and some other sophisticated instrumental method such as graphite furnace atomic absorption spectrometry (GF-AAS) and inductively coupled plasma mass spectrometry (ICP-MS), and it can be further lowered down to 0.03 ng mL^{− 1} by increasing the trapping time to 4 min. The platinum coating was stable for 300 firings without sensitivity loss. Interference and its alleviation were studied in detail. The proposed method was applied to the determination of tellurium in several geological standard reference materials, and the results were found in good agreement with the certified values.     

Determination of Traces of Chromium in Foods by Solvent Extraction Flame Atomic Absorption Spectrometry

ABSTRACT

A simple methodology for Cr(III) determination in foods was developed through flame atomic absorption spectrometry with air/acetylene after a fast oxidation of Cr(III) with KM_nO₄ and pre-concentration of Cr(VI) in MIK as C_rO₂CI₂. A limit of detection and limit of quantification (LOQ), respectively, of 4 μg/Kg and 13 μg/Kg Cr(III) were obtained in commercialized foods in São Paulo, Brazil. Two certificated samples as well as some food samples were analyzed with good results. A study of sample treatment showed that the dry ash method is the best.     

Some causes of bending of analytical curves in atomic emission flame spectrometry

Factors affecting the shape of analytical curves in atomic emission flame spectrometry are discussed. Equations are presented by which the effect on the analytical curve of self-absorption, ionization, compound formation, variation in solution flow rate and atomization efficiency, entrance optics, and multiple spectral lines can be considered quantitatively. Theoretical and experimental curves are compared for Na introduced as aqueous NaCI solution into H₂/air, H₂/O₂, and C₂H₂/O₂ flames. The portion dealing with the effect of ionization, compound formation, and variation in solution flow rate and atomization efficiency on the atomic concentration in the flame applies as well to atomic absorption and atomic fluorescence flame spectrometry.     

Use of multivariate curve resolution for determination of chromium in tanning samples using sequential injection analysis

We report a method for determining total chromium in tanning samples using sequential injection analysis (SIA) with a diode-array spectrophotometric detector. With a suitable analytical sequence CrO₄^2– is converted to Cr₂O₇^2– inside the tubes of the SIA system, after total oxidation of chromium(III). A data matrix is obtained and analysed by several chemometric techniques based on multivariate analysis: principal components analysis, simple-to-use interactive self-modelling mixture analysis, and multivariate curve resolution-alternating least-squares. We studied several samples from different stages of a tanning process. Two of these samples were easily oxidized but the others needed more extreme conditions. The analytical sequence prepared, which was based on obtaining a pH gradient and used H₂SO₄ as reagent, is valid and independent of the level of oxidation needed for the sample. We established a calibration model and evaluated the figures of merit. In some samples we found interferents. With this method the amounts of chromium in each sample were quantified and the results were statistically similar to those obtained by use of the reference method, atomic absorption spectrometry.