Multi-element neutron activation analysis measurements towards the geochemistry of particulate matter exchange between continent—Atmosphere—Ocean

Sampling of marine aerosol and ocean water particulate matter yields very small quantities of material. INAA is used for routine analysis since it provides measurements of as many as 25 elements and permits multiple use of the small samples. Results are given for the mean elemental composition of Atlantic marine aerosols and oceanic suspended matter. Such analyses are essential for the interpretation of global geochemical cycles.     

The impact of uncertainty in the elemental composition of the certified reference material on gamma spectrometry

In this paper the impact of the uncertainty in the elemental composition of the certified reference material (CRM) used for absolute efficiency calculations in gamma spectrometry is investigated. The method involved the use of semi-empirical modeling using solid angle concepts. The samples involved were a standard Jamaican soil, four bauxite reference samples from NIST and a standard ICRU reference material configuration simulating the calibrating CRM. The results indicate that at gamma energies below 60 keV, the impact on the bauxite reference samples and local soil samples resulted in errors up to 43 and 70 % respectively when the elemental composition of the efficiency calibrating reference sample was ignored. A set of equations for correcting the errors introduced were developed. The modeling of a theoretical soil type validated the process of ashing soils for low energy gamma spectrometry due to the extremely high errors introduced by the element carbon.     

Energy dispersive X-ray fluorescence analysis of marine pollution indicators

The present work shows a methodology for the application of EDXRF with a X-ray tube, in the analysis of elements in the following matrices: microalgae, marine algae, marine sediments and corals. Various methods were applied: one using a relative external standard, a fundamental parameters method, an absolute method based on elemental sensitivity, a method which used X-ray fluorescence excitation measured in the back side of the sample for low contents heavy elements determination and a TRXRF method. The thin layer samples were prepared using a plastic resin. The analyzed samples of marine algae, marine sediments and corals belong to a marine ecosystem from the North of Havana City, the most affected area by natural metereological phenomena and human impact.     

Determination of vitamin B12 as cobalt by electrothermal atomic absorption spectrometry using the solid sampling technique

Summary An investigation has been carried out to establish a rapid method for the determination of vitamin B₁₂ as cobalt in solid pharmaceutical samples by electrothermal atomization atomic absorption spectrometry with the solid sampling technique using an inner miniature cup. Calibration graphs of peak area versus mass of the element were constructed by use of a synthetic reference material (SyRM). The SyRM is prepared by coprecipitation of cobalt ions with magnesium(II) 8-quinolinate. In order to determine the accuracy of the proposed method, three pharmaceutical preparations were analyzed according to the proposed method using standardization against the SyRM and the results obtained compared with those when solutions of the same samples were analyzed by other techniques. There is good agreement between the results obtained from the proposed and the other method. The detection limit for cobalt in a solid pharmaceutical preparation is 0.15 ng/mg (i.e. 4 ng/mg of vitamin B₁₂) for a typical sample mass of 1.0 mg.

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Bestimmung von Vitamin B₁₂ als Cobalt mit Hilfe der elektrothermischen Feststoff-AAS

     

Chemical and isotopic compositions of bottled waters sold in Korea: chemical enrichment and isotopic fractionation by desalination

A total of 54 Korean bottled waters were investigated to characterize their origins and types using elemental and isotopic composition, as well as to identify elemental and isotopic changes in desalinated marine water that arise due to desalination. The different types of bottled water displayed a wide pH range (3.42 to 7.21). The elemental compositions of still and sparkling waters were quite similar, whereas desalinated marine water was clearly distinguished by its high concentrations of Ca, Mg, B, and Cl. In addition, desalinated marine water had much higher isotope ratios of oxygen and hydrogen (-0.5 and -2‰, respectively) than still and sparkling waters (-8.4 and -57‰). The elemental composition of desalinated marine water was adjusted through post-treatment procedures; in particular, boron was greatly enriched during desalination processes. The carbon isotope compositions of dissolved inorganic carbon (δ(13)C(DIC) values) varied widely according to the origins of the bottled waters (-25.6 to -13.6‰ for still water, -31.2 to -26.7‰ for sparkling water, and -24.1 to -6.3‰ for desalinated marine water). This indicates that carbon isotopes in dissolved inorganic carbon are significantly fractionated by desalination processes and re-modified through post-treatment procedures. The results suggest that combined elemental and stable isotopic tracers are useful for identifying the origin of bottled water, verifying elemental and isotopic modifications during desalination processes, and characterizing various water types of bottled waters.     

Elemental concentrations in sediments of the Patras Harbour, Greece, using INAA, ICP-MS and AAS

Twenty marine sediment samples, selected downcore from six sediment cores, which were retrieved from the Patras Harbour, were studied for their elemental composition using three analytical techniques: INAA, ICP-MS and AAS. Standard reference materials were used to verify the accuracy of the analysis techniques. In total, the concentrations of 30 major, minor and trace elements were measured. The vertical distribution of most elements in the examined cores could be characterized as relatively uniform. The eastern part of the harbour seems to be more polluted in respect to some elements (Ag, Br, Cd, Cr, Cu, Pb and Zn) compared to the western one. The concentrations of a number of elements (As, Cd, Cr, Cu, Ni, Pb and Zn) determined in the sediment samples of the present work are discussed regarding to those obtained from other harbours in the world and compared against sediment quality guidelines (SQGs) to assess the ecotoxicological significance of the sediment contaminants to benthic biota.     

Determination of elemental selenium and pyrite-selenium in sediments

A method is described for the selective determination of concentrations of elemental selenium and pyrite-selenium in sediments. A 1 M sodium sulfite solution is used to solubilize elemental selenium and a Cr(II) solution releases selenium in pyrite. The accuracy of the methods was evaluated by using various selenium compounds. The detection limits for the elemental and pyrite-selenium procedures are 0.001 and 0.025 μg Se per gram of sediment, respectively. The relative standard deviationis < 10% for elemental selenium and < 16% for pyrite-selenium. These and other procedures were used for selenium speciation in marine and freshwater sediments.     

A comparative study of laser induced breakdown spectroscopy analysis for element concentrations in aluminum alloy using artificial neural networks and calibration methods

A comparative study of analysis methods (traditional calibration method and artificial neural networks (ANN) prediction method) for laser induced breakdown spectroscopy (LIBS) data of different Al alloy samples was performed. In the calibration method, the intensity of the analyte lines obtained from different samples are plotted against their concentration to form calibration curves for different elements from which the concentrations of unknown elements were deduced by comparing its LIBS signal with the calibration curves. Using ANN, an artificial neural network model is trained with a set of input data of known composition samples. The trained neural network is then used to predict the elemental concentration from the test spectra. The present results reveal that artificial neural networks are capable of predicting values better than traditional method in most cases.     

Characterization of soil,sediment, and wastewater samples from hydraulic fracturing processes using the comparative NAA method

Regulatory monitoring of oil and gas development requires the accurate multi-elemental analysis of wellbore samples on a regular basis. In this study, an unconventional method, comparative neutron activation analysis (comparative NAA), was applied for the multi-elemental characterization of solid and liquid hydraulic fracturing samples at the ppm level. The obtained values from three wastewater samples were compared with the most probable values determined via an inter-laboratory study, which involved 15 different laboratories from the United States, Canada, and Germany. The comparison showed that 15 out of 19 comparative NAA trace element concentration values were considered acceptable, providing a new technique to determine elemental concentrations in high salinity hydraulic fracturing samples.

     

Elemental Analysis of Copper-Zinc Ores by Total Reflection X-Ray Fluorescence using Nonaqueous Suspensions

Novel rapid determination of copper-zinc ore elemental composition by total reflection X-ray fluorescence (TXRF) is proposed. Approaches for solid state sample analysis by TXRF are provided. The sample preparation is chosen to obtain the suspensions in ethylene glycol. The optimum suspension preparation conditions (sample mass, volume of dispersion medium) and the measurement conditions (internal standard element, spectra acquisition time) were determined. The sedimentation stability of suspensions was studied. It was found that the suspensions remain stable for approximately 2?min, which is sufficiently long for the sampling the suspension. The proposed technique allows determining the elemental composition of solid ore samples without sample digestion. The sample preparation time takes approximately 20?min. The relative standard deviation of the analytical results did not exceed 10%.     

Sampling strategies for the analysis of glass fragments by LA-ICP-MS Part I. Micro-homogeneity study of glass and its application to the interpretation of forensic evidence

The authors have previously reported the use of laser ablation ICP-MS as a powerful analytical tool for elemental analysis of glass. LA is a simpler, faster and less intrusive sample introduction method than the conventional solution ICP-MS. Due to the minute amount of material removed in LA (∼300 ng, 50 μm crater size), the analyst should be aware of special sampling considerations such as characterization of the glass fragments originating from the “known” source, fragment size and selection of the area and surface of ablation.The purpose of this work was to evaluate the micro-homogeneity of the elemental composition of glass samples commonly found in crime scenes like containers, architectural windows and windshields. The set of glasses under study was comprised of 56 fragments originated from glass containers, 28 fragments from automobile windshields and 20 fragments from architectural windowpanes. All fragments were selected with a size smaller than 2 mm² in order to simulate the typical glass fragments transferred from the crime scenarios. A Nd:YAG laser, 266 nm, flat top beam profile was used in single point mode sampling 50 μm spot size for 50 s at 10 Hz (500 shots). In this study, ²⁹Si was used as an internal standard and the standard reference material, SRM NIST 612, was used as a single point external calibrator. In addition, SRM 621 was used as another control standard for the containers set and SRM 1831 for the automobile and architectural window sets due to their very similar matrix with the samples of interest. For each set of glasses, the mean values and standard deviation of 10 replicates (n = 10) of a single fragment were compared with the values obtained from 10 (n = 10) different fragments of glass within the area of interest in order to evaluate whether or not the variation within a glass was bigger than the variation due to the method. In addition, a subset of tempered glasses was evaluated to perform an elemental composition profile within different depths of the fragments. Single shot (one laser pulse per analysis) was also evaluated and its limitations for the forensic analysis of glass are also presented. The results show that float glass is homogenous even at the micro-range level allowing LA-ICP-MS as an alternative technique to perform elemental analysis of glass. However, the variation of elemental composition of headlamps and containers is larger over the source than the instrumental variation due to inherent heterogeneity and therefore specific statistical methods are recommended to compare the glass samples.     

Organic matter in onshore cretaceous chalks and its variations,investigated by pyrolysis-mass spectrometry

Organic matter from twelve onshore Cretaceous chalks, present in amounts of about 0.002–0.1% by weight, was extracted in the form of humic acids. Curie-point pyrolysis-mass spectrometry, with factor analysis of the spectra, disclosed three principal modes of variation in the organic composition, as reflected by well-defined homologous groups of products. The principal of these factors was closely similar to a previously found soil factor and was characterized by well-defined groups of aromatic hydrocarbon products. Comparisons with infrared spectra and elemental composition suggest that it corresponds to early diagenetic alteration, probably involving microbial activity in the original sediments. A second factor, characterized by products of lignin and porphyrin origin, represents a contribution from terrestrial plant sources. This, however, is negligible in all but two of the samples. The third factor, characterized by amino acid products, is likely to reflect the contribution of marine organisms, particularly plankton, to the original organic sediment.     

Neutron activation analysis on sediments from Victoria Land,Antarctica: multi-elemental characterization of potential atmospheric dust sources

The elemental composition of 40 samples of mineral sediments collected in Victoria Land, Antarctica, in correspondence of ice-free sites, is presented. Concentration of 36 elements was determined by instrumental neutron activation analysis, INAA. The selection of 6 standard reference materials and the development of a specific analytical procedure allowed to reduce measurements uncertainties and to verify the reproducibility of the results. The decision to analyze sediment samples from Victoria Land ice-free areas is related to recent investigations regarding mineral dust content in the TALos Dome ICE core (159°11′E; 72°49′S, East Antarctica, Victoria Land), in which a coarse local fraction of dust was recognized. The characterization of Antarctic potential source areas of atmospheric mineral dust is the first step to identify the active sources of dust for the Talos Dome area and to reconstruct the atmospheric pathways followed by air masses in this region during different climatic periods. Principal components analysis was used to identify elements and samples correlations; attention was paid specially to rare earth elements (REE) and incompatible/compatible elements (ICE) in respect to iron, which proved to be the most discriminating elemental groups. The analysis of REE and ICE concentration profiles supported evidences of chemical weathering in ice-free areas of Victoria Land, whereas cold and dry climate conditions of the Talos Dome area and in general of East Antarctica.     

Comparison between X-ray fluorescence and inductively coupled plasma atomic emission spectrometry in the analysis of sediment samples

Two multielemental analytical techniques, X-ray fluorescence analysis (XRF) and inductively coupled plasma atomic emission spectrometry (ICP-AES) were used for the analysis of the elemental composition of sediment samples from a marsh and standard reference materials. The sediment samples were pretreated with different methods which are widely used in practice. A comparison was made not only between the concentrations obtained by the different methods, but also between the statistical conclusions derived from the processing of the experimental results. Good agreement was found for some elements, e.g. Mn, Zn and Sr, while the concentrations and the statistical conclusions were shown to depend on the analytical method used in the case of other elements, e.g. Fe and Zr.     

Characteristics of the aerosol particulates in the atmosphere in an urban environment at Faisalabad, Pakistan

Summary The deposition of trace and major elements from the atmosphere to the ground is an important factor for plants, animals and humans as well. Total suspended particulate matter was measured by a standard gravimetric technique. A scanning electron microscope was used for the evaluation of the size distribution and morphological structures of the aerosol particulates trapped on the surface of filter paper. The aerosol particulates were studied by a scanning electron microscope at various magnification. The trace elemental composition in the atmosphere of Faisalabad was studied by using instrumental neutron activation analysis (INAA) and atomic absorption spectrometry (AAS). Concentrations of 23 trace elements and a major one were determined in samples of aerosol particulates collected during a longe sampling period in the atmosphere at Faisalabad, Pakistan. Their amount was two times higher than the limits adopted by the U.S. Environmental Protection Agency for the urban environment.     

Study of properties of the glass batch melting filter dust

The filter dust from the container glass production was studied by the X-Ray powder diffraction, differential thermal analysis (DTA), X-Ray fluorescent spectroscopy, and Raman spectroscopy. The analysis of the elemental composition indicated that the major portion (≈96 wt%) of filter dust is comprised of sulfates. Predominant abundance of sodium sulfate was confirmed by comparative DTA of investigated filter dust. The characteristic redox property (COD—Chemical Oxygen Demand) was determined. The raw materials used in manufacturing of container glass in Vetropack Nem?ová with 0, 25, 50, 75 or 100 wt% of filter dust as a substitution of sulfate raw material were used for the preparation of samples of glass batch. Thermal properties of prepared samples were characterized by means of DTA. The substitution of sulfate raw material by filter dust does not significantly affect the thermal properties of the examined glass batches and consequently the course of the glass melting.     

Composition of lignocellulosic surfaces: comments on the interpretation of XPS spectra

The surface compositions of lignocellulosic materials are critical to their end use performance. X-ray photoelectron spectroscopy (XPS) measures the elemental composition sampling of a very thin surface layer, and has long been used to assess the surface composition of dry lignocellulosic materials. The method is based on the quantification of carbon and oxygen XPS peak sizes and shapes, but care is necessary to minimize the effects of surface contamination and degradation. We review the XPS method, and present a simplified approach to estimate the surface lignin content of extractive-free samples. The approach corrects for surface contamination and degradation by measuring the XPS signal of a cellulose standard under the same conditions as the lignin-containing samples. The method is illustrated using XPS results for a series of extracted softwood kraft pulps.     

Self-absorption model in quantitative laser induced breakdown spectroscopy measurements on soils and sediments

Application of laser induced breakdown spectroscopy (LIBS) in the quantitative analysis of elemental composition of soils with different origins and Antarctic marine sediments has been considered. The analytical method followed includes the usual plasma modeling at local thermal equilibrium (LTE) based on average temperature and electron density values, as well as spectra normalization, introduced in order to reduce the effects related both to the substrate optical and thermal properties and to the influence of laser parameters on quantitative data. The computational algorithm takes into account only atomic species and their first ionization states, which is sufficient at the plasma temperature measured in the experiments. Calibration curves are finally generated for each element of interest measured on certified samples with different provenience and matrix composition. In this paper a model is developed which takes into account the effects responsible for non-linearities in the relationship between line intensity and elemental concentration. The model properly includes line re-absorption and contributions from space regions with different plasma densities. Its application permits us to obtain the correlation coefficients between the LIBS measured and certified concentration of each element analyzed. These coefficients, specific for a given experimental layout and atomic lines data base, are successively applied in analytical LIBS measurements allowing for the direct determination of a single element concentration in any sample, regardless of its unknown matrix composition. The LIBS method presented here was tested on a priori unknown samples, and gave uncertainties in concentration varying from 15 to 40% over a large concentration range covering several orders of magnitude. The measuring error depends on element type, on the concentration value and also on the number of certified samples used for the initial calibration. The present results are already significant for some field application, such as on-board marine sediment analysis where a significant matrix variation with layer depth is common.     

Neutron activation analysis of flints from the edwards formation

Procedures for instrumental neutron activation analysis have been developed and used on flint samples collected from the Edwards Formation in Texas. Each of the samples was analyzed for Mn, Ca, V, Al, Sc, Co, Fe, As, and K. USGS standard rocks AUG-1, GSP-1, and G-2 were also analyzed in order to test the reliability of this technique. Means and standard deviations of each element determined were calculated. The elemental values ranged from 0.03 ppm for scandium to 1500 ppm for aluminium. Based on relative elemental abundances, the rocks could be classified into two types of flint. This information suggests elemental inhomogeneity in the Edwards Formation.     

XRF induced by PIXE: Comparison with PIXE

Two different modes of sample excitation have been used for elemental analysis of thin standard reference materials and of chemical standards with known composition. PIXE /2.5 MeV protons/ and XRF induced by PIXE, will be called XRF-PIXE /2.5 MeV protons on Mo primary target/. The same samples were alternatively exposed to protons and X-ray beams. The sensitivities under standard running conditions are determined for both an XRF-PIXE and a PIXE analysis system. It is shown that the sensitivity of the PIXE spectrometer depends strongly on the sample matrix, whereas the XRF-PIXE sensitivity is rather constant with respect to different kinds of samples. In addition, the advantages of one mode of excitation on the other are discussed. It is shown that XRF-PIXE can be a useful complement to PIXE analysis.