Decomposition methods in elemental trace analysis

Frequently, systematic errors in the decomposition step of a trace analytical multistage procedure lead to erroneous results in spite of the fact that expensive and powerful apparatus has been used for the determination. Of the numerous decomposition methods that have been published only a few meet the requirements of modern trace analysis.     

Monitoring ground-level air for trace analysis: methods and results

Trace analysis enables the sensitive detection of radionuclide concentrations in ground-level air in the range of microbecquerel per cubic meter (Bq m^–3). Typical sampling intervals of less than one day up to a few days can be used in routine operation. Trace analysis measurements are performed in the framework of the German Integrated Measuring and Information system (IMIS) and the International Monitoring System (IMS) used for verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Within the environmental monitoring programmes of the German IMIS the Federal Office for Radiation Protection (BfS) performs measurements of aerosol-bound radionuclides and of radioactive noble gases in the atmosphere. Aerosols are collected on filters with high-volume air samplers and analysed by -spectrometry, -spectrometry, and integral measurements of -activity, with preceding radiochemical separation. Noble gas samples from 15 sites world-wide are analysed to observe the ⁸⁵Kr-release from nuclear fuel reprocessing plants and from seven sites in Germany to monitor the ¹³³Xe emitted from nuclear power plants. As part of the International Monitoring System (IMS) of the CTBT an automatic aerosol sampling and measuring system and an automatic noble gas sampling and measuring system will be operated by the BfS at Mount Schauinsland near Freiburg. Because of its expertise in noble gas measurements the BfS had been chosen to perform an intercomparison experiment in the BfS laboratory in Freiburg with several automatic noble gas sampling and measurement systems before their installation at IMS sites. To establish quality-assurance programmes for trace analysis performed for the German IMIS close collaboration between the involved German institutions has been established. First steps have been taken to expand cooperation to other European laboratories. Informal data exchange already occurs between trace-analysis laboratories in Europe (Ring of Five) and helps in cases of enhanced activity concentrations to get a rapid overview of the radiological situation and to identify possible sources.     

Comparison of three methods for trace analysis of polycyclics

Summary Several analytical techniques for the determination of polycyclic aromatic hydrocarbons in air have been evaluated. Two solvents, benzene and cyclohexane, were compared for their efficacy in the preliminary preparation of the air sample. To identify and measure the polycyclics, the techniques of ultraviolet absorption and fluorescence were used. Air sample extracts were analyzed with and without prior Chromatographic separation. A rapid Chromatographic procedure using benzene as elutant was employed for the first time. The extract aliquot or eluate fraction was chromatographed on fully activated alumina using benzene as the eluting solvent. BaP and BkF are eluted from such a column in 30 minutes or less in a total eluate volume of perhaps 50 ml and the two hydrocarbons are determined by fluorescence emission. Work in progress suggests that benzene may be replaced in this application by the less toxic toluene.By any method used the BkF values found were in good agreement. The agreement between the various BaP values was poor, suggesting not all were of equal validity. The highest, and also least accurate, BaP values seem to be associated with the use of benzene as extractant, or ultraviolet absorption as a measuring technique.

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Zusammenfassung Verschiedene Analysenverfahren zur Bestimmung polycyklischer aromatischer Kohlenwasserstoffe in Luft wurden ausgearbeitet. Benzol und Cyklohexan wurden hinsichtlich ihrer Wirksamkeit als Lösungsmittel bei der Vorbereitung der Luftproben verglichen. Zur Identifizierung und Messung der polycyklischen Substanzen wurde die UV-Absorption und die Fluoreszenz herangezogen. Die Luftprobenextrakte wurden mit und ohne vorherige chromatographische Auftrennung analysiert. Bin rasches chromatographisches Verfahren mit Benzol als Elutionsmittel wurde erstmals verwendet. Extraktanteil oder Eluatfraktion wurden auf hochaktivem Aluminiumoxid chromatographiert und mit Benzol eluiert. Benzo(a)perylen (BaP) und Benzo(k)fluoranthen (BkF) werden aus einer solchen Säule in 30 Minuten mit etwa 50 ml eluiert und durch Fluoreszenzmessung bestimmt. Es scheint naheliegend, statt Benzol das weniger toxische Toluol zur Elution zu verwenden. Die nach jeder Methode erhaltenen BkF-Werte stimmen gut überein im Gegensatz zu den BaP-Werten. Die höchsten und gleichzeitig wenigst genauen BaP-Werte treten offenbar auf, wenn Benzol als Extraktionsmittel und UV-Absorption zur Messung verwendet werden.

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Presented at the Anachem Conference, Detroit, Mich., U. S. A., October 11, 1966.     

Voltammetric methods for speciation analysis of trace metals in natural waters

Trace metals play an important role in the regulation of primary productivity and phytoplankton community composition. Metal species directly affects the biogeochemical cycling processes, transport, fate, bioavailability and toxicity of trace metals. Therefore, developing powerful methods for metal speciation analysis is very useful for research in a range of fields, including chemical and environmental analysis. Voltammetric methods, such as anodic stripping voltammetry (ASV) and competing ligand exchange-adsorptive cathodic stripping voltammetry (CLE-AdCSV), have been widely adopted for speciation analysis of metals in different natural aquatic systems. This paper provides an overview of the theory of voltammetric methods and their application for metal speciation analysis in natural waters, with a particular focus on current voltammetric methods for the discrimination of labile/inert fractions, redox species and covalently bound species. Speciation analysis of typical trace metals in natural waters including Fe, Cu, Zn, Cd, and Pb are presented and discussed in detail, with future perspectives for metal speciation analysis using voltammetric methods also discussed. This review can elaborate the particular knowledge of theory, merits, application and future challenge of voltammetric methods for speciation analysis of trace metals in natural waters.     

Nuclear-based methods for the analysis of trace element pollutants in human hair

The trace element composition of human hair is a suitable indicator of exposure to trace element pollutants. During the implementation of an international research programme, coordinated by the IAEA, on the use of nuclear methods for detecting trace element pollutants in hair, much valuable information was collected both on normal levels of trace elements and on increased levels caused by pollution. As a result of reviewing and comparing the data, interesting observations relating to the spread of concentrations were made. Standardized procedures were elaborated for a number of analytical techniques as well as for pre-analytical preparations in the analysis of hair. Paper presented at the Second Meeting on Nuclear Analytical Procedures, Dresden (GDR), 19 to 23 March 1979.     

The complementary use of radioanalytical methods and trace analysis methods for the characterisation of environmental IAEA reference materials

The IAEA laboratories have access to both nuclear analytical methods and conventional instrumental methods for trace analysis for the characterisation of its environmental and biological reference materials. A technical concept integrating the homogeneity data, the recommended test portion mass and the uncertainty on the trace element concentrations is explored using a combination of INAA, XRF, ICP-MS, ICP-AES, and AAS. The above approach is illustrated by selected examples of reference materials currently under evaluation for their trace element content. They include some or all of the following elements Al, As, Br, Ca, Cd, Co, Cr, Cs, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, Pb, Rb, Se, Sr, Th, U, Zn in environmental biomonitor organisms (lichen, algae) and air dust filters.     

Speciation methods of actinides in trace concentrations

The development of actinide speciation methods in the environment is discussed. The results on speciation and migration of radionuclides in near-surface and deep conditions at the Krasnoyarsk mining and chemical plant and at the Production Association ‘Mayak’ (southern Ural) are reported. For surface conditions, the mobile plutonium fraction is mostly associated with inorganic complexes (carbonate) of the higher plutonium oxidation state, while less mobile fraction is associated with low-soluble Pu(IV) complexes with humic acids. The mobile fraction of americium consists of complexes with low molecular weight fulvic acids of non-specific nature with molecular weights lower than 10 kDa. Plutonium and americium behaviour in deep conditions is governed by colloid migration. To cite this article: A.P. Novikov et al., C. R. Chimie 7 (2004).

Résumé

Méthodes de spéciation des actinides en traces. Le développement de méthodes pour la spéciation des actinides dans l’environnement est discuté. Nous présentons des résultats concernant la spéciation et la migration des radionucléides dans des conditions de sub-surface et en milieux géologiques profonds à la mine de Krasnoyarsk et à l’usine chimique de Mayak (Oural du Sud). En conditions de sub-surface, la fraction mobile contient essentiellement des complexes inorganiques (carbonates) de Pu dans ses degrés d’oxydation élevés, tandis que la fraction moins mobile contient des complexes insolubles du Pu(IV), avec des acides humiques. La fraction mobile de Am comporte des complexes d’acides fulviques de nature non précisée, mais d’une masse molaire inférieure à 10 kDa. En conditions de milieu profond, le comportement de Am et de Pu est influencé par la migration des colloïdes. Pour citer cet article : A.P. Novikov et al., C. R. Chimie 7 (2004).     

Substoichiometry in trace analysis

Substoichiometric methods of analysis are simple in principle and involve the addition of a smaller amount of reagent than is required for complete reaction with the element to be determined. They can be used with great effect in trace analysis.     

Optimization studies for reliable trace metal analysis in sediments by atomic absorption spectrometric methods

Summary Sediments act as traps for metals introduced into the aquatic environment. Studies on the total metal contents have been performed with sediments from rivers, lakes, estuaries and coastal zones. The sediments were decomposed under pressure with a 31 mixture of HNO₃/HCl. The determinations were performed by atomic absorption spectrometry in appropriate specific modes (flame, graphite furnace, cold vapour mode, hydride system). The methods were optimized and verified with regard to precision and accuracy for the determination of 12 metals or metalloids by the use of some now available Control and Reference Materials.

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Optimierungsstudien zur richtigen Metall-Spurenanalyse in Sedimenten mittels atomabsorptionsspektrometrischer Methoden

Zusammenfassung Sedimente speichern Metalle, die in die aquatische Umwelt eingebracht werden. Untersuchungen über die Metall-Totalgehalte wurden durchgeführt mit Fluß-, See-, Ästuar- und Küstensedimenten. Die Sedimente wurden einem Druckaufschluß mit einem 31-Gemisch von HNO₃/HCl unterworfen. Die Bestimmungen der Spurenmetalle erfolgten anschließend mit der Atomabsorptionsspektrometrie unter Anwendung geeigneter, spezifischer Techniken (Flamme, Graphitrohrküvette, Kaltdampfverfahren, Hydridsystem). Die Methoden wurden optimiert und bezüglich Präzision und Richtigkeit der Bestimmung von 12 Metallen oder Metalloiden verifiziert durch den Einsatz einiger jetzt verfügbarer Kontroll- und Referenzmaterialien.

     

NAA and ICP-MS: A comparison between two methods for trace and ultra-trace element analysis

NAA and ICP-MS are both highly sensitive methods for multi-element trace-and ultra-trace element determination. A comparison between analytical figures of merit of both methods is made. Both methods have specific advantages that put them beyond competition for certain applications. It is concluded that ICP-MS can replace NAA for many routine analyses. NAA remains essential as a highly reliable and accurate reference method.     

Mass spectrometry in trace analysis

This report is an opinion piece arising from the response to the 1996 ASMS Fall Workshop “Limits to Confirmation, Quantitation, and Detection.” The two subjects that generated the most heated discussion at the Workshop were the criteria for qualitative confirmation of target analytes and those for defining and measuring limits of detection and of quantitation. A reportorial account of the Workshop has been published previously (Baldwin, R.; et al. J. Am. Soc. Mass Spectrom. 1997, 8, 1180–1190). The purpose of the present work is to (1) attempt to reconcile the sometimes highly divergent views expressed by some of the invited Workshop speakers and (2) provide some impetus toward a consensus approach to the dual problems of analyte identification and operational definitions of limits of detection and quantitation for application to trace analysis using chromatography with mass spectrometric detection. In view of the wide range of analytical problems dealt with by modern mass spectrometrists and the varied contexts in which these activities are undertaken (including regulatory requirements and possible legal challenges), both issues are addressed using the concept of fitness for purpose. It is proposed that an appropriate goal is not to define a set of universally applicable criteria, but rather to recommend guidelines for establishing integrated analytical methods best suited to the particular purpose and context.     

Validation of ion chromatographic methods for the trace analysis of ions in pharmacopoeial grades of water

Ion chromatography was investigated as an alternative technique to conventional pharmacopoeial methods for the determination of inorganic anions and cations in pharmacopoeial grades of water. These methods were validated by generating data on parameters such as specificity, linearity, precision, accuracy, sensitivity, ruggedness and stability of solution. The validation data demonstrate that ion chromatography is a viable alternative technique to current pharmacopoeial methods which enables automation of pharmacopoeial water analyses.     

Comments on the primary and scatter dose-spread kernels used for convolution methods

The basic primary and scatter dose-spread kernels used for convolution methods are usually produced by Monte Carlo simulations with the interaction point forced to the center of a large water phantom. However, it is still not clear whether such Monte Carlo based kernels allow accurate dose calculations with a wide range of field sizes and depths, especially in thorax phantoms. Using the differential primary and scatter concept, this paper proposes another type of basic kernel, with which perfectly accurate primary and scatter absorbed dose calculations can be performed under conditions that the beam is parallel, the incident beam intensity is uniform within and zero outside the field, and the primary beam attenuation coefficient along raylines is not a function of depth and off-axis distance.     

Electrogravimetric trace analysis on a piezoelectric detector

A novel and rapid electroanalytical method for the determination of cadmium at micromolar concentrations is described. The method utilizes the piezoelectric effect to follow small mass changes which result from electrodeposition.     

Microcomputers in electrochemical trace elemental analysis

The advantages of incorporating digital computers in devices for electrochemical trace elemental analysis are discussed on the basis of examples from the literature. Apart from easing data interpretation, the digital computer may control and monitor electrode processes at a high interaction frequency. For elements undergoing reversible electrode reactions, the resolution and sensitivity of electrochemical techniques can be improved by such rapid real-time interaction. Moreover, for quasi-reversible systems, the application of computerized broad-band potential excitation and simultaneous monitoring of broad band relaxation signals, permits rapid extraction of analytical information from data which represent the electrode process more accurately than do traditional single-frequency a.c. polarographic data.     

Comparison of different types of filters for atmospheric trace element analysis by three analytical methods

Different atmospheric aerosol samples were collected on three types of filters. From both of the loaded and clean areas of each kind of filter, different disks were cut and investigated by XRF, PIXE and scanning electron microscopy (SEM). The blank concentration values of the elements Al, Si, P, S, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Br and Pb in the three types of filter are discussed. It is found that for trace elemental analysis, the Nuclepore membrane filters are the most suitable for sampling. These filters have much lower blank element concentrations than the glass fiber and ash free filters. It was found also that PIXE is a more reliable analytical technique for atmospheric aerosol particles than the other methods used.