Analysis of the Arctic aerosol for a ten year period using various neutron activation analysis methods

During the past decade we have determined the concentrations of a variety of trace elements in the Arctic aerosol by using themal and epithemal neutron activation analysis (NAA). More recently we have employed Compton suppression NAA to lower the detection limits for radionuclides that are characteristic of single or mainly single gamma-ray emission. Using these various methods, we have been able to use elements such as indium and silicon. Furthermore we have achieved extremely low detection limits for iodine, arsenic and antimony. The usefulness of these NAA methods are discussed in a large sampling program that incorporates more than one thousand samples.     

Direct determination of trace elements in niobium,tantalum and their oxides by inductively coupled plasma atomic emission spectrometry after microwave dissolution

Analytical schemes for the determination of trace elements in high-purity niobium, tantalum and their oxides are proposed. The schemes are based on microwave dissolution of the metals and oxides followed by inductively coupled plasma atomic emission spectrometry (ICP-AES) determination of impurities in the solutions. The possibilities of interelement and off-peak background corrections in ICP-AES analysis are discussed. The accuracy of the results obtained is confirmed by the determination of trace elements after a matrix sorption separation procedure. For a number of elements, a comparison of the results obtained by ICP-AES without and with the matrix separation procedure and by electrothermal atomic absorption spectrometry (ETAAS) shows good agreement. The limits of detection for direct ICP-AES determination are in the range 0.4*1.0 μg g⁻¹ for Ba, Ca, Fe, Mg, Mn, Y and La; between 2.0 and 10.0 μ g⁻¹ for B, Cd, Co, Cr, Cu, Hf, Mo, Na, Nb, Ni, Pb, Sr, Ti, Zr and Ta; and for K, Sb and W a detection limit of 20 μ g⁻¹ is achieved. The schemes proposed are intended for rapid routine analysis.     

Determination of trace impurities in tantalum powder and its compounds by inductively coupled plasma optical emission spectrometry using solvent extraction

A procedure was developed for the analysis of 18 trace impurity elements in capacitor-grade tantalum powder (Ta), potassium tantalum fluoride (K₂TaF₇), and tantalum pentoxide (Ta₂O₅) using inductively coupled plasma optical emission spectrometry (ICP-OES). The detection limits achieved were in the ppb levels. The samples were dissolved in hydrofluoric acid (HF) in a microwave digestion system and the Ta matrix was extracted using cyclo hexanone. The impurity traces remained almost completely in the aqueous phase. The text was submitted by the authors in English.     

Fast simultaneous determination of niobium and tantalum by Kalman Filter analysis with flow injection chemiluminescence method.

A fast and highly efficient Kalman Filter analysis-flow injection chemiluminescence (FI-CL) method was developed to simultaneously determine trace amounts of niobium and tantalum in geological samples. The method, without the boring process of separation and dear instruments, is suitable for field scene analysis. The mixed chemiluminescence kinetic curve was analyzed by a Kalman Filter (KF) in this method to realize the simultaneous determination of niobium and tantalum. Possible interference elements in the determination were investigated. Under the selected conditions, the detection limits (3sigma, n = 11) of niobium(V) and tantalum(V) were 2.1 x 10(-3) microg g(-1) and 4.0 x 10(-3) microg g(-1), respectively, and the relative standard deviations were 4.9% and 3.3% (n = 9). The method was applied to the determination of niobium and tantalum in geological samples with satisfactory results.     

A microbatch anion-exchange technique for matrix separation

Summary A rapid and simple one-vessel microbatch anionexchange method has been developed for matrix separation prior to the AAS determination of the trace elements. The method can be applied to the separation of matrix elements which are strongly sorbed on anion exchangers, e.g. gold, palladium, bismuth a.o. The method was illustrated by the flame or ET-AAS determination of 20 trace elements in pure gold. The limits of detection were from 0.002 to 0.4 g/g, the RSD from 3 to 8% depending on the trace element.     

Applications of nuclear analytical techniques in environmental research. Plenary lecture.

Among nuclear analytical techniques, neutron activation analysis (NAA) is particularly useful for environmental studies. It affords low detection limits for many elements, high specificity and few sources of systematic error, which means that high accuracy is attainable. Neutron activation analysis is particularly useful for trace and ultra-trace analysis of environmental samples (water, soils, rocks and biological material). In trace element work associated with pollution, instrumental NAA is a powerful technique for multi-element surveys, in particular when combined with other spectroscopic techniques. Nuclear techniques, as with most analytical techniques, cannot be used to distinguish between different physico-chemical forms of an element per se. When used in combination with appropriate separation techniques, however, nuclear techniques can provide valuable information about trace element speciation in environmental and biological systems. From dynamic tracer experiments, i.e., addition of chemically well defined labelled compounds to environmental systems, valuable information can be obtained on the distribution of species and on microchemical processes influencing the physico-chemical forms. In these laboratories, speciation studies on trace elements in natural waters have been carried out by using instrumental NAA in combination with physical separation techniques, such as dialysis and ultrafiltration, in situ and in the laboratory. Dynamic radiotracer experiments have provided important information about processes influencing the speciation of trace elements in aquatic systems. Sequential extraction techniques have proved to be useful in studies on sediments and soils when combined with NAA. Sequential extractions also provide significant information about the physico-chemical behaviour of radionuclides supplied to natural soils from the Chernobyl accident.     

Optimisation of plasma techniques for trace analysis of refractory metals

Besides atomic absorption spectrometry, the plasma techniques can be seen as state-of-the-art instrumentation in an industrial laboratory for the analysis of trace elements today. For the analysis of refractory metals, e.g. Mo and W, the determination limits which can be reached by ICP-AES techniques are mainly restricted by the spectral background of the matrix. Advantages and disadvantages of sequential and simultaneous detection as well as different methods of evaluation, such as Kaiman filtering and multiple component spectral fitting, are discussed. The results are compared with trace matrix separation techniques and on-line coupling of ion chromatography with ICP-AES and ICP-MS. Furthermore, the limitations of all techniques with respect to their applicability for routine analysis, especially the complexity of sample preparation, degree of automation, time consumption and cost are shown. With respect to the detection capability, TMS with ICP-MS end determination is the most powerful technique, but for routine analysis simultaneous multielement determination from the matrix is favourable.     

Analysis of tantalum by ICP-AES involving trace-matrix separation

Summary A trace-matrix separation technique for the analysis of high-purity tantalum by ICP-AES has been developed to overcome the difficulties caused by the line-richness of this matrix. The procedure is based on the extraction of tantalum with diantipyrylmethane from 12 mol/l HF in dichloroethane. The extraction behaviour of 35 elements has been investigated from which 25 can quantitatively be separated with a residual matrix concentration <0.01% at 1 g sample portion. The achievable limits of detection for ICP-AES are between 0.02 g/g and 10 g/g. The method was applied to the analysis of a high-purity tantalum sample. For a number of elements, the results of this technique are compared with those of other techniques whereby, in general, a good agreement was achieved.     

Application of on-line HPLC-ICP-MS for the determination of the nuclide abundances of lanthanides produced via spallation reactions in an irradiated tantalum target of a spallation neutron source

An analytical procedure has been developed for the determination of spallation nuclides in an irradiated tantalum target using HPLC coupled on-line to ICP-MS after dissolution and separation of the tantalum matrix. Pieces of tantalum were taken from different locations of the irradiated tantalum target which had been used as the target material in a spallation neutron source. Tantalum was dissolved in a HNO₃/HF mixture and the tantalum matrix was separated by liquid-liquid extraction so that only the spallation nuclides were left in the sample solutions. The major fraction of the spallation nuclides in the tantalum target are lanthanide metals in the μg g^–1 concentration range determined in the present study. Additional reaction products are formed by the irradiation of trace impurities in the original tantalum target. The nuclide abundances of the lanthanide metals measured in the tantalum target differ significantly from the natural isotopic composition so that a lot of isobaric interferences of long-lived radionuclides and stable isotopes in the mass spectrum are to be expected. Therefore, all the lanthanide metals had to be separated chemically prior to their mass spectrometric determination. The separation of all rare earth elements was performed by ion chromatography on-line to ICP-MS. The nuclide abundances of each lanthanide were determined using a sensitive double-focusing sector field inductively coupled plasma mass spectrometer. The nuclide abundances of the lanthanides in the irradiated tantalum target calculated theoretically and the experimental results obtained by on-line HPLC-ICP-MS proved to be in good agreement.     

Determination of impurity elements in high-purity solid precursors based on tantalum pentoxide by inductively coupled plasma mass spectrometry

Conditions for the inductively coupled plasma mass-spectrometric (ICP MS) analysis of high-purity tantalum pentoxide and tantalum pentoxide doped with rare-earth elements without the separation of a sample matrix from analytes (Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Sn, W, Gd, Dy, Er, and Pb) were determined. The metrological parameters of ICP MS analysis (accuracy, precision, and detection limits) were calculated. It was established that, in the analysis of test sample solutions with tantalum concentrations higher than 30 mg/L, a matrix effect appeared: the intensity of the measured ion current of analytes decreased against the background of a high concentration of sample matrix (tantalum) ions. This caused a proportional underestimation of the results of analysis. It was shown that it is reasonable to plot calibration functions against the background of a solution containing no more than 30 mg/L of tantalum ions. The results of the ICP MS analysis were compared with X-ray fluorescence (XRF) and optical emission spectrometry (OES) analysis data and calculation data on the amounts of admixtures introduced into tantalum pentoxide at the stage of the extraction preparation of a precursor.     

Comparative PGAA and NAA results of geological samples and standards

Concentrations of major and trace elements in volcanic rock and soil samples, including geological standard reference materials, were determined by neutron activation analysis (NAA) and prompt gamma activation analysis (PGAA), both using the k ₀-standardization method. The paper highlights the different experimental procedures, such as sample preparation, data collection and spectrum evaluation. In geological samples, PGAA gives precise results for major elements (Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K and—as a unique method—for H), for some of the light trace elements as B and Cl, as well as for Sc, S, Cr, Co, Ni, Cd, Nd, Sm and Gd. NAA is sensitive for the rare earth elements, and for many major (Ti, Al, Fe, Mn, Mg, Ca, Na, K) and trace elements (e.g.: Sc, V, Cr, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Zr, As, Sb, Ce, Ba, Hf, Ta, W). For most major elements the results obtained by the two methods show good agreement. The comparison of the results obtained for trace elements is not always possible, since PGAA is less sensitive and concentrations are often below its detection limits. Nevertheless, the complementarity of NAA and PGAA allows nearly panoramic analysis of geological materials.     

Inorganic trace analysis by mass spectrometry

Mass spectrometric methods for the trace analysis of inorganic materials with their ability to provide a very sensitive multielemental analysis have been established for the determination of trace and ultratrace elements in high-purity materials (metals, semiconductors and insulators), in different technical samples (e.g. alloys, pure chemicals, ceramics, thin films, ion-implanted semiconductors), in environmental samples (waters, soils, biological and medical materials) and geological samples. Whereas such techniques as spark source mass spectrometry (SSMS), laser ionization mass spectrometry (LIMS), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), glow discharge mass spectrometry (GDMS), secondary ion mass spectrometry (SIMS) and inductively coupled plasma mass spectrometry (ICP-MS) have multielemental capability, other methods such as thermal ionization mass spectrometry (TIMS), accelerator mass spectrometry (AMS) and resonance ionization mass spectrometry (RIMS) have been used for sensitive mono- or oligoelemental ultratrace analysis (and precise determination of isotopic ratios) in solid samples. The limits of detection for chemical elements using these mass spectrometric techniques are in the low ng g⁻¹ concentration range. The quantification of the analytical results of mass spectrometric methods is sometimes difficult due to a lack of matrix-fitted multielement standard reference materials (SRMs) for many solid samples. Therefore, owing to the simple quantification procedure of the aqueous solution, inductively coupled plasma mass spectrometry (ICP-MS) is being increasingly used for the characterization of solid samples after sample dissolution. ICP-MS is often combined with special sample introduction equipment (e.g. flow injection, hydride generation, high performance liquid chromatography (HPLC) or electrothermal vaporization) or an off-line matrix separation and enrichment of trace impurities (especially for characterization of high-purity materials and environmental samples) is used in order to improve the detection limits of trace elements. Furthermore, the determination of chemical elements in the trace and ultratrace concentration range is often difficult and can be disturbed through mass interferences of analyte ions by molecular ions at the same nominal mass. By applying double-focusing sector field mass spectrometry at the required mass resolution—by the mass spectrometric separation of molecular ions from the analyte ions—it is often possible to overcome these interference problems. Commercial instrumental equipment, the capability (detection limits, accuracy, precision) and the analytical application fields of mass spectrometric methods for the determination of trace and ultratrace elements and for surface analysis are discussed.     

Characterization of simulated vitrified highly active waste and its leachates by neutron activation

Neutron activation analysis (NAA) methods have been developed for the simultaneous determinations of multielement concentrations in various types of glass and their leachates. The epithermal instrumental NAA (EINAA) method involves the irradiation of samples in a Cd-shielded site for 2–5 min in order to determine levels of of up to 13 elements through their short-lived nuclides. Another 15 elements can be measured via their long-lived nuclides using conventional instrumental NAA (INAA). Accuracy of the methods have been evaluated by analyzing certified reference materials. The limits of detection for all elements are reported. The methods have been applied to sodium borosilicate and sodium calcium aluminosilicate glass samples in order evaluate their suitability as a host matrix for immobilizing high level radioactive waste.     

Verbundverfahren zur Multielement-Spurenbestimmung in hochreinem Chrom nach Spuren—Matrix-Trennung

(Simultaneous determination of trace elements in high-purity chromium by inductively-coupled plasma/atomic emission spectrometry after matrix separation.) The production of high-purity metals requires routine determinations of elements in the ng g^?1 range. Procedures based on wet chemical separation of matrix and trace elements followed by inductively-coupled plasma/atomic emission spectrometry are suitable. The separation of 19 trace metals (Be, Bi, Ca, Cd, Co, Cu, Fe, La, Mg, Mn, Nb, Ni, Pb, Ta, Ti, Th, U, Zn and Zr) from high-purity chromium powder is described. The powder is dissolved in hydrochloric acid and oxidized with perchloric acid or alkaline hydrogen peroxide, and the trace elements are precipitated at pH 11–13 and collected on cellulose loaded with indium hydroxide or on cellulose-Hyphan. The detection limits of the total procedure vary from 10 ng g^?1 for cadmium to 600 ng g^?1 for zinc.     

Investigations concerning the analysis of high-purity metals (Cd, Cu, Ga and Zn) by high resolution inductively coupled plasma mass spectrometry

High resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) in combination with a micro concentric nebulizer was studied in order to evaluate its suitability for the certification of the content of trace elements in high-purity metals. About 30 trace elements (analytes) were determined using solutions of high-purity Cd, Cu, Ga and Zn. The concentration levels of these matrices were varied as an experimental parameter. HR-ICP-MS was demonstrated to be very versatile and of high analytical performance. Effects of matrix concentrations on the analytical sensitivities and on the detection limits were investigated to find out optimal working conditions and to distiguish between different sources of matrix influences on sensitivities. As an example the gallium matrix was studied to obtain information about the matrix depositions on the cones of the mass spectrometer inlet system, using scanning electron microscopy and spectroscopical methods, including Raman spectroscopy.     

Microliter sample introduction into an inductively-coupled plasma by electrothermal carbon cup vaporization

An atomic emission spectrometric system is described for quantifying trace elements in microvolume samples. The system involves vaporizing the sample by electrothermal carbon cup vaporization followed by the atomization and excitation of the vapor cloud in an inductively coupled plasma (i.c.p.). The detection limits for 21 elements in 10-μl samples are at ng ml^-1 and sub-ng ml^-1 levels with linear dynamic ranges of over four orders of magnitude. Carbon cups coated with pyrolytic graphite are overcoated with tantalum carbide. These cups have resulted in improved detection levels (performances) for Al, As, Bi, Co, Cu and Sn relative to those not containing tantalum. However, cups not treated with tantalum are superior for Au, Cd, Ge, Hg, K, Li, Mg, Mn, Rb and Zn. Comparisons between the two types of carbon cups are presented and discussed. Results also are compared with literature values available for other electrothermal vaporization systems.     

On-line ion-exchange separation and determination of niobium,tantalum, tungsten,zirconium and hafnium in high-purity iron by flow injection inductively coupled plasma mass spectrometry

A study was made to investigate the feasibility of using an anion-exchange resin for on-line separation of trace amounts of niobium, tantalum, tungsten, zirconium and hafnium from iron matrix samples. The incorporation of a micro-column packed with Dowex 1X8-100 ion-exchange resin into a flow injection system is presented. The detection was done with inductively coupled plasma mass spectrometry (ICP-MS). The sample treatment, optimization of analytical variables and measurable concentration levels are discussed. Recoveries from standard additions to a high-purity iron were for all the analytes close to 100%, with relative standard deviations ranging from 0.7 to 3.0%. The limits of quantification (10 s_n−1) calculated from a 5% (m/v) iron sample solution were 8, 5, 14, 12 and 10 ng g⁻¹ for Nb, Ta, W, Zr and Hf, respectively. The accuracy of the proposed method was tested by determining these elements in Euronorm-CRM 098-1 reference material. Recoveries from 0.250 g test portions of the above reference material spiked with 2.5 and with 12.5 ng each of the five analytes are reported.     

Spectral interference study of uranium on other analytes by using CCD based ICP-AES

Due to the multi-electronic nature, uranium is having line rich emission spectra and is expected to interfere during the determination of analytes at the trace level in uranium matrix. Therefore, chemical separation of uranium followed by the determination of trace metallic impurities in the raffinate by ICP-AES is generally adopted procedure in nuclear industries. There is restriction on choosing alternate analytical lines of elements by photomultiplier tube based ICP-AES associated with the polychromator while monochromator needs significant time to scan different analytical lines of all the elements. Since charged coupled detector (CCD) consists of array of pixels, it is having more option in choosing alternative analytical lines of the analytes. Therefore, an attempt was made to study the spectral interference of uranium on different analytical lines of analytes viz. Al, Ga, In, Si, Li, Ti, Mg, Sr, K, Ce, Nd, Lu, Sc, V, Er, Y, Ba, Bi, Pb, W, La, Tl, Sn, Yb, Mo, Sb, Pr and Zr; and the correction factors were evaluated (where ever necessary) using CCD based ICP-AES technique. The sensitivity and the detection limits of the analytical channels of the elements in presence of uranium matrix were calculated. The present study also deals with the identification of suitable analytical lines of uranium and its detection limits.     

Activation analysis: The most important method for control of purity of semiconductor silicon

NAA and CPAA are the most sensitive analytical tools for the determination of residual impurities in semiconductor silicon. Extremely small detection limits are found by measuring the activity in an underground laboratory. The accuracy and reliability of the methods were checked by several comparisons: interlaboratory comparison on NAA, another CPAA with IR-spectrometry as well as comparison of NAA-results, obtained instrumentally and by chemical separation.     

Speciation problems solved with NAA: Some actual cases for Hg,V, Cr,As and Se

The evaluation of the eco-toxic consequences of heavy metals on the biosphere requires assessment of their biological effects. This involves the determination of the different ionic species and the various chemical forms of each element. For many elements, the usual electrochemical methods for the analysis of different chemical species do not meet the required sensitivity; ppm or even ppb concentration ranges represent often the actual content of many matrices. For many elements as Hg, V, Cr, As, and Se one of the most sensitive method of trace determinations down to the ppb level is the NAA. Unfortunately this method gives information only on the total number of nuclei present, regardless to their outer structure and chemical forms. In this work, some examples are given of the feasibility of NAA to the determination of trace amounts of different chemical species of some heavy metals, when coupled to specific separation procedures.