Multielement content of coal by neutron activation analysis techniques

Due to the interaction with components present in natural waters, radionuclides may be present in different physico-chemical forms, varying in size, charge and density. The distribution pattern will influence the transport, mobility and biological uptake of the radionuclides. Size fractionation based on hollow fiber is useful for the determination of the size distribution pattern of radionuclides in natural waters. Furthermore, a continuous mixing and separation system has been developed for the investigation of the association of radionuclides with naturally occurring colloids. Results based on radionuclides in waste water from the Forsmark nuclear power plant, Sweden, will illustrate the potential usefulness of the technique.     

Multielement analysis of aluminium by NAA and ICP/AES

The results of neutron activation analysis (NAA) and inductively coupled plasma atomic emission spectrometry (ICP/AES) are compared for aluminium samples in the purity range from 99.7 to 99.998%. The advantages of each method towards the determination of 25 elements is discussed.     

Element analysis of inhomogeneous samples by laser ablation ICP mass spectrometry

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been used for the determination of selected elements in heterogeneous powdered soils. The precision of the method essentially depends on the homogeneity of the samples. Therefore the influence of sample inhomogeneity on the precision of analytical results has been checked. The statistical evaluation was carried out using a correlation function. In the context of the described experiments, it is necessary to analyze a volume of about 20 mm³ in order to obtain reliable information on the bulk composition of the heterogeneous samples. This corresponds to about 50 craters, each with a depth of 1 mm. The results can be used to calculate certain analytical parameters, particularly the sample homogeneity, depending on the necessary analytical volume and the representative mass for the quantitative analysis under previously defined conditions. In addition to these calculations, analytical experiments have been carried out which confirm the applicability of this approach.     

Comparison of matrix effects in inductively coupled plasma using laser ablation and solution nebulization for dry and wet plasma conditions

Matrix effects of calcium in inductively coupled plasma-atomic emission spectrometry were investigated. Matrix effects were studied by monitoring the excitation conditions of the plasma using Zn ionic to atomic spectral line intensity ratios. Dry and wet inductively coupled plasmas with robust and non-robust conditions were compared. Laser ablation and solution nebulization sample introduction were used to produce the dry and wet plasma conditions, respectively. Low (0.6 l/min) and high (1.0 l/min) carrier gas flow rates were used to produce the robust and non-robust conditions, respectively. No differences in the trend of matrix effects for dry and wet plasmas were observed at vertical positions above normal observation height (>8 mm height above load coil) for low and high carrier gas flow rates. However, matrix effects in the lower part of the plasma (<8 mm height above load coil) were significantly different between dry and wet plasmas when a high carrier gas flow was used. The differences are likely due to the desolvation process.     

Multielement comparison of instrumental neutron activation analysis techniques using reference materials

Several instrumental neutron activation analysis techniques (parametric, comparative, and k_o-standardization) are evaluated using three reference materials. Each technique is applied to National Institute of Standards and Technology standard reference materials, SRM 1577a (Bovine Liver) and SRM 2704 (Buffalo River Sediment), and the United States Geological Survey standard BHVO-1 (Hawaiian Basalt Rock). Identical (but not optimum) irradiation, decay, and counting schemes are employed with each technique to provide a basis for comparison and to determine sensitivities in a routine irradiation scheme. Fifty-one elements are used in this comparison; however, several elements are not detected in the reference materials due to rigid analytical conditions (e.g., insufficient length of irradiation or activity for radioisotope of interest decaying below the lower limit of detection before counting interval). Most elements are normally distributed around certified or consensus values with a standard deviation of 10%. For some elements, discrepancies are observed and discussed. The accuracy, precision, and sensitivity of each technique are discussed by comparing the analytical results to consensus values for the Hawaiian Basalt Rock to demonstrate the diversity of multielement applications.     

Determination of trace impurities in high purity copper using sector-field ICP-MS: continuous nebulization, flow injection analysis and laser ablation

High resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) was applied for multielement-determination in high-purity copper (approx. 99.99%). The samples were introduced into the instrument by three different introduction systems, which were studied with respect to high accuracy, low detection limits and fast analysis: continuous nebulization (CN), flow injection analysis (FIA) and laser ablation (LA). The trueness of the applied method was checked by the analysis of high-purity copper reference material (BCR Cu074). All values obtained for this CRM using CN were in the range of the stated uncertainty for the 9 elements determined: Ag, As, Bi, Cr, Fe, Ni, Pb, Sb, and Sn with contents in the range of 0.5–13 μg/g. Another approach for checking the trueness of the method was to compare the results obtained by this method characterizing the purity of a 4N (99.99% copper content) copper material with those obtained by application of electrothermal atomic absorption spectrometry (ET-AAS) and inductively coupled plasma optical emission spectrometry (ICP-OES). For further characterizing, the concentrations of 49 elements were found in this material below detection limits of HR-ICP-MS in the range of low μg/kg and sub μg/kg. The combination of HR-ICP-MS and a flow injection analysis system (FIAS) improved the robustness of the system in regard to high matrix concentrations. Therefore, matrix concentrations up to 4 g/L could be used for liquid analysis and detection limits were lowered by a factor of 2–5. A calibration method for bulk analysis with laser ablation was developed with doped copper powder as pressed pellets for calibration standards. This method proved to be an excellent fast semi-quantitative method, which was less time consuming in comparison with the analysis of liquids. After application of correction factors the deviation between the results obtained by laser ablation and by analysis of liquids was ≈ 15% for most elements. The method offered the possibility to check for potential losses of analytes occurring during the wet chemical operations. Received: 23 November 1998 / Revised: 25 February 1999 / Accepted: 2 March 1999     

Determination of trace impurities in high purity copper using sector-field ICP-MS: continuous nebulization, flow injection analysis and laser ablation

High resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) was applied for multielement-determination in high-purity copper (approx. 99.99%). The samples were introduced into the instrument by three different introduction systems, which were studied with respect to high accuracy, low detection limits and fast analysis: continuous nebulization (CN), flow injection analysis (FIA) and laser ablation (LA). The trueness of the applied method was checked by the analysis of high-purity copper reference material (BCR Cu074). All values obtained for this CRM using CN were in the range of the stated uncertainty for the 9 elements determined: Ag, As, Bi, Cr, Fe, Ni, Pb, Sb, and Sn with contents in the range of 0.5–13 μg/g. Another approach for checking the trueness of the method was to compare the results obtained by this method characterizing the purity of a 4N (99.99% copper content) copper material with those obtained by application of electrothermal atomic absorption spectrometry (ET-AAS) and inductively coupled plasma optical emission spectrometry (ICP-OES). For further characterizing, the concentrations of 49 elements were found in this material below detection limits of HR-ICP-MS in the range of low μg/kg and sub μg/kg. The combination of HR-ICP-MS and a flow injection analysis system (FIAS) improved the robustness of the system in regard to high matrix concentrations. Therefore, matrix concentrations up to 4 g/L could be used for liquid analysis and detection limits were lowered by a factor of 2–5. A calibration method for bulk analysis with laser ablation was developed with doped copper powder as pressed pellets for calibration standards. This method proved to be an excellent fast semi-quantitative method, which was less time consuming in comparison with the analysis of liquids. After application of correction factors the deviation between the results obtained by laser ablation and by analysis of liquids was ≈ 15% for most elements. The method offered the possibility to check for potential losses of analytes occurring during the wet chemical operations. Received: 23 November 1998 / Revised: 25 February 1999 / Accepted: 2 March 1999     

Strategies for the analysis of coal by laser ablation inductively coupled plasma mass spectroscopy

A comparison between a laser-induced breakdown spectrometry-partial least squares (LIBS-PLS) method and methods based on some well-known techniques, such as induced-coupled plasma-atomic emission spectrometry (ICP-AES), flame atomic absorption spectrometry (FAAS), and atomic scanning microscopy (ASM) is presented in order to both validate the content of gold and silver in alloys to be used as solid standards and develop an alternative to the established methods for the hallmark of gold and silver in jewelry pieces. 17 alloys with gold concentrations ranging from 100 to 50% and 8 alloys with silver concentrations between 100 and 80% and variable concentrations of other metals usually present in jewels were used as solid standards in LIBS in order to develop a method as general as possible. The results obtained in the analysis of some alloys (9 for gold and 7 for silver) show that the proposed method is comparable with the official one.     

Nigerian coal analysis by PIXE and RBS techniques

PIXE and RBS techniques were employed for the measurement of the concentrations of the major, minor and trace elements in Nigerian coal samples from a major deposit. The samples were irradiated with 2.55 MeV protons from the 3 MeV tandem accelerator (NEC 3 UDH) in Lund. The PIXE results are reported and compared with an earlier work on Nigerian coal using FNAA and INAA analytical techniques while the RBS results are compared with ASTM previous results. The results show that Nigerian coals have a low (0.82–0.99)% sulfur content. This is quite important for pollution control reasons.     

Multielement photon activation analysis of coal samples using a Compton suppressed Ge(Li) detector

Multielement photon activation analysis has been carried out using a Compton suppressed Ge(Li) detector. The irradiated samples were N.B.S. standard reference coals and ashes. An increase in sensitivity by as much as a factor of three is attainable for some elements and this is especially valuable when analysing coals with low trace metal concentrations like N.B.S. reference material 1635.     

Direct analysis of polymer pyrolysis using laser microprobe techniques

A laser microprobe-mass analysis technique has been developed which enables the overall course of polymer decomposition processes to be directly followed. Volatile pyrolysis products evolved during laser-vaporization of the polymer substrate are immediately formed into a molecular beam and mass analyzed. Modulated molecular beam techniques are utilized to provide increased detection sensitivity and to aid in the analysis of complex mass spectra by providing a means to directly discriminate parent ions from fragment ions. Elimination of intermediate product collection stages permits the time-resolved behavior of the polymer decomposition process to be investigated. Results are presented for rigid and plasticized polyvinyl chloride, a polyoxymethylene copolymer and a polyester elastomer block copolymer.     

Characterization of nuclear fuels by ICP mass-spectrometric techniques

Isotopic analyses of radioactive materials such as irradiated nuclear fuel are of major importance for the optimization of the nuclear fuel cycle and for safeguard aspects. Among the mass-spectrometric techniques available, inductively coupled plasma mass spectrometry (ICP-MS) and thermal ionization mass spectrometry are the most frequently applied methods for nuclear applications. Because of the low detection limits, the ability to analyze the isotopic composition of the elements and the applicability of the techniques for measuring stable as well as radioactive nuclides with similar sensitivity, both mass-spectrometric techniques are an excellent amendment to classical radioactivity counting methods. The paper describes selected applications of multicollector ICP-MS in combination with chromatographic separation techniques and laser ablation for the isotopic analysis of irradiated nuclear fuels. The advantages and limitations of the selected analytical technique for the characterization of such a heterogeneous sample matrix are discussed.     

Multielement analysis of lichen by instrumental neutron activation analysis

Lichen (species Trypethelium Eluteriae) is analysed for different elements. Nondestructive instrumental neutron activation analysis is employed for the multielemental analysis. Gamma-ray spectrometry is used for the identification and quantitative estimation of elements. Concentrations of 24 elements are reported. Gamma-ray spectrum of the lichen irradiated for 16 hours, delayed for 10 days, and counted for 10 hours on a 50 cm³ coaxial Ge(Li) detector is given.     

Quantitation methods using laser ablation ICP-MS

Laser Ablation ICP-MS offers the capability of direct analysis of conductive and non-conductive samples. However the quantitation capabilities of LA-ICP-MS are often questioned. In order to qualify the term quantitation, different methods, appropriate for laser ablation, are discussed. Measurements on different sample matrices were performed both semiquantitatively and quantitatively using standards with the same matrix. Additionally, the use of an internal standard, a minor isotope of the matrix element or a known concentration of a trace or a minor element can be selected as an aid to quantitation. In cases where there is no certified element concentration available, a user value for the LA-ICP-MS sensitivity can be chosen. These different methods of quantitation are compared and the rationale behind each approach is discussed.     

Mass spectrometry of DNA mixtures by laser ablation from frozen aqueous solution.

We report time-of-flight mass spectra of test mixtures of six single-stranded DNA segments. The segments range in size from 8 to 60 nucleotides (molecular weight range 2413 to 18,602 Da). The best mass spectra were obtained by pulsed laser ablation of thin frozen films of an aqueous solution of the mixture from an oxidized copper substrate. These mass spectra are dominated by the molecular-ion peak for each DNA segment, and show little evidence of fragmentation, peak broadening or cluster formation. In contrast, mass spectra obtained using UV laser ablation from an anthranilic acid matrix yield broad peaks with evidence of fragmentation, and DNA segments longer than 26 nucleotides are difficult to detect.     

Elemental composition of laser ablation aerosol particles deposited in the transport tube to an ICP

The element ratios in aerosol particles produced by laser ablation (λ=266 nm, pulse length: 5 ns) of brass and steel in Ar and He and deposited in different segments of the transport tube to an ICP have been measured by ICP-MS. The data are compared with the ratios obtained by a corresponding bulk analysis. For brass, the element compositions of the aerosol particles deposited in different parts of the tube deviated from the bulk and varied along the tube. For steel, moderate agreement of the element ratios in the aerosols and the bulk was found. It is also shown that elemental ratios measured on-line by laser ablation ICP-MS with the laser-produced aerosol should not be calibrated by elemental ratios obtained with wet aerosols from aqueous solutions of the bulk.     

Multielement ultratrace analysis in tungsten using secondary ion mass spectrometry

Summary The ever increasing demands on properties of materials creates a trend also towards ultrapure products. Characterization of these materials is only possible with modern, highly sophisticated analytical techniques such as activation analysis and mass spectrometry, particularly SSMS, SIMS and GDMS [1].Analytical strategies were developed for the determination of about 40 elements in a tungsten matrix with high-performance SIMS. Difficulties like the elimination of interferences had to be overcome. Extrapolated detection limits were established in the range of pg/g (alkali metals, halides) to ng/g (e. g., Ta, Th).Depth profiling and ion imaging gave additional information about the lateral and the depth distribution of the elements.

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Multielementepurenanalyse in Wolfram mittels SIMS

     

Multielement analysis of food spices by instrumental neutron activation analysis

Twenty-four elements in six food spices were estimated by non-destructive instrumental neutron activation analysis. The problems in determining Cu were discussed.     

Multielement analysis by sequential instrumental and radiochemical neutron activation

We measured 37 elements in six USGS geological camples and one NBS biological orchard leaf (OL) sample, using sequential INAA and radiochemical group separation coupled with high resolution, high efficiency Ge(Li), and a Ge(Li) with anticoincidence shields. The elemental concentrations in these samples vary over three orders of magnitude. Our results agree very well with the reported values. The rare earth values in PCC-1 are 2–4 times lower than the reported values. Precise REE patterns are defined in USGS samples, which are characteristic of the total rock types. The REE pattern in OL is identical to the mineral apatite. In addition to the possibility that OL may be contaminated by local soil, it is also possible that the uptake of REE trace elements by plants from soil is perhaps dominated by accessory mineral such as apatite, or plants take up the REE from bulk soil in a preferential manner as a smooth function of the REE ionic radii.     

Investigation of plasmas produced by laser ablation using single and double pulses for food analysis demonstrated by probing potato skins

We report on investigations of plasmas produced by laser ablation of fresh potatoes using infrared nanosecond laser radiation. A twin laser system consisting of two Nd:YAG oscillators was used to generate single or double pulses of adjustable interpulse delay. The potatoes were irradiated under ambient air with moderate pulse energies of about 10 mJ. The expansion dynamics of the ablation plume was characterized using fast imaging with a gated camera. In addition, time-resolved optical emission spectroscopy was applied to study the spectral line emission of the various plasma species. The electron density was deduced from Stark broadening, and the plasma temperature was inferred from the relative emission intensities of spectral lines. The relative concentrations of metals were estimated from the comparison of the measured emission spectra to the spectral radiance computed for a plasma in local thermal equilibrium. It is shown that the plasma produced by double pulses has a larger volume and a lower density. These properties lead to an increase of the signal-to-noise ratio by a factor of 2 and thus to an improved measurement sensitivity.