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Eingeladener Vortrag
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Normally, in analytical GD-MS, the doubly charged metallic ion signals from the sample are several orders of magnitude less than the corresponding singly charged signals. However, we have observed that using a neon plasma, the M++ signals of some elements, which have double ionization energies close to the first ionization energy of neon, are of the same order as the M+ signal. Doubly charged ions may be produced directly in the discharge cell by electron ionization (EI), and also by two electron Penning ionization (TEP), but these processes cannot explain the above effect. In this paper, we suggest that an additional process named as ‘Charge Transfer and Ionization’ (CTI) produces such ions either in their ionic ground state or in an excited state. To confirm that this process is typical of the discharges used in GD-MS and not an artefact of any particular form of cell and ion extraction system, we have carried out comprehensive experimental measurements using three different GD-MS instruments, viz., Nu Astrum, VG9000 and ELEMENT GD and our results provide clear evidence for CTI. This is the first time the process has been identified as an ionization process in analytical GD-MS. CTI must be differentiated from Asymmetric Charge Transfer (ACT), which is a “selective” process and requires a close energy match (e.g. ΔE < 0.5 eV for a strong effect). On the other hand, CTI is “non-selective” in the sense that a close energy match is not required (e.g. a strong effect is observed with ΔE ∼ 2 eV), although the process only occurs for a limited number of elements, depending on the plasma gas used and the total energy required to doubly ionize the metallic atom.
A candidate material for the use as primary standard for nickel determination was characterized with respect to total purity. For element determination a pure material can serve as primary standard. However, real world materials are never absolutely pure, hence the total purity of such materials need to be determined experimentally. A reasonable target uncertainty for the purity statement is 10-4 relative. Usually, the purer the material, the easier it is to achieve this target uncertainty. There are two basic ways in order to be able to establish a total purity statement. One is to determine the main component of a high purity material by a direct method such as coulometry, gravimetry or titrimetry. However, these methods are not selective enough for one element and therefore require certain efforts to analyse the material with respect to impurities with interfering analytes. Moreover, to reach the defined target uncertainty is not easy or often impossible to achieve. The second approach is to determine the sum of all possible impurities (as mass fraction) and to subtract it from the ideal purity of 100 % (1 kg/kg). In principle all impurities (all elements not being the matrix element), metals and non-metals must be considered. In this work both approaches to determine the total purity of the nickel material were followed and compared.
The primary (solid) standards are usually used to prepare primary calibration solutions to which secondary and lower order calibration solutions are linked.
Die Einwerbung von Drittmitteln wird immer mehr zur zwingenden Notwendigkeit, wenn man Forschung betreiben möchte. Drittmittel sorgen nicht dafür, dass man zusätzliches Geld für die Forschung ausgeben kann, wie das früher einmal der Fall war, sie werden mehr und mehr zur Grundbedingung für Forschung überhaupt. Zu den Drittmitteln zählen insbesondere Projektmittel der Forschungsförderung des Bundes, der Länder, der EU und anderer öffentlicher Stellen, der Wirtschaft zur Durchführung von Forschungsaufträgen sowie der Deutschen Forschungsgemeinschaft. Sie machen bereits einen entscheidenden Teil des Budgets von Universitäten (25-30%, Tendenz steigend) und Forschungseinrichtungen aus. In den Präsidien und Rektoraten werden Stabsstellen eingerichtet, um mögliche Fördertöpfe zu finden und erfolgreiches Formulieren von Anträgen zu unterstützen und die Formalien der Antragstellung zu optimieren. Je mehr Drittmittel eine Einheit einwirbt, mit umso mehr Grundmitteln darf sie rechnen. Dem hohen Zeitaufwand der Wissenschaftler für das Schreiben von Anträgen stehen jedoch immer niedrigere Bewilligungsquoten gegenüber. Sehr umfangreiche Projekte mit sehr vielen Partnern scheinen immer schwieriger zu begründen zu sein. Lange Bearbeitungszeiten bis zur Bewilligung von Projekten und Laufzeiten von 4 Jahren stehen im Widerspruch zu den Planungszeiträumen für Forschungsprojekte im Industrielabor. Im Zeichen immer stärker geforderter Interdisziplinarität müssen andere Wege gefunden werden, um die Stärken einer Messtechnik überzeugend einzubringen.
Was ist zu tun? In diesem Diskussionsbeitrag werden Informationen zusammengetragen, um Fördermöglichkeiten der Grundlagenforschung und Applikationen von GD-techniken auszuloten und die Kooperation von Forschungseinrichtungen und Industriepartnern praktikabel zu realisieren.
Reference materials are essential, when the accuracy and reliability of measurement results need to be guaranteed in order to generate confidence in the analysis.
These materials are frequently used for determining measurement uncertainty, for validation of methods, suitability testing and quality assurance. Especially direct solid sampling methods require reference materials for calibration.
They guarantee that measurement results can be compared to recognized reference values.
This presentation gives an overview about the use of GDMS in various certification procedures. Because it represents a fast, sensitive, multielement analyses technique without extensive sample preparation it plays a special role for the purity determination of high purity standards. Various calibration strategies and the preparation of traceable matrix matched calibration standards will be discussed.
For the certification of analyte content in matrix materials mainly techniques with solvent sample preparation are used. Here GD-MS is used to identify possible loss or contamination with analytes during the sample preparation step. Typically used acids to dissolve matrices lead to interferences in the ICP- mass spectrometric detection of various analytes and their quantification. Here GD-MS as direct method can also add an important contribution in the certification process.
Analytical glow discharges with optical (GD-OES) and mass spectrometric (GD-MS) detection are able to obtain depth resolved information about the light elements hydrogen, carbon, nitrogen and oxygen in solid samples, where most of the other analytical techniques fail. However, the interpretation or even quantification of the measured signals is still very challenging. Problems arise due to physical effects (plasma processes such as the ‘Hydrogen effect’, the Doppler effect, self absorption or diffusion of hydrogen in the sample during sputtering) chemical effects(e.g. formation of compounds with argon or the matrix, poisoning of the sample or gettering) as well as instrumental difficulties (e.g. of the sensitivity, calibration and vacuum quality)..
The GD techniques are direct solid sampling methods and require reference materials for calibration. Unfortunately the list of available certified reference materials (CRM) suited for calibration of light elements in different matrix is relatively short Therefore, sintered materials doped with the analytes H2, O2 and N2 were produced at IFW Dresden and applied as calibration standards for hydrogen, oxygen and nitrogen. Due to the high analyte concentration added, it is very likely that the real concentration agree well with the added amount of light elements in the corresponding phases. The validation of the determination of the light element concentration in the sintered samples was possible in some cases only due to the lack of suitable techniques. This fact proves the need for the development of a reliable quantification of light elements by GDS.
A systematic dependence of the sputtering rate on the composition was found and can be explained by basic principles.
Using mixtures of TiH2 and ZrH2 with Cu the ratio of hydrogen and Cu lines has a good correlation with the corresponding concentration ratio. The hydrogen emission yield however decreases over 0.3 m% hydrogen and finally the hydrogen intensity may even decrease. This behaviour can be explained by a very similar quenching of the hydrogen and copper intensity caused by the hydrogen effect. First experiments with GD-MS show no saturation of the hydrogen ion current and thus confirm the quenching of the emission yield in GD-OES.
Sintered material for the oxygen calibration (Al2O3, CuO, Cu2O and MgO mixed with Cu, Al and Mg) confirmed the blue line shift effect at O I 130.22 nm, first time reported by Köster 2009 [1]. The effect is more pronounced at Mg than in Al and Cu, which due to line interference leads to a matrix dependent EY. This effect is negligible at O I 777.19 nm and the EY is matrix independent. Using GD-MS first promising results for the calibration of oxygen with these sintered samples could be obtained, when the sputtering rate was included in the evaluation.
More recently also sintered material for nitrogen calibration (AlN mixed with Al and Si3N4 mixed with Cu) was produced and points to a matrix independent emission yield of nitrogen
Die Junganalytiker der Fachgruppe „Analytische Chemie“ der Gesellschaft Deutscher Chemiker (GDCh) veranstalteten in Zusammenarbeit mit der BAM eine Herbstschule zum Thema „Qualitätssicherung in der Analytischen Chemie“.
Schulung v.a. für Doktoranden, um den Umgang mit qualitätssichernden Aspekte bei der Entwicklung analytischer Methoden zu erlernen.
Die wichtigsten Grundbegriffe der Genauigkeitskenngrößen von Messgrößen werden in diesem Vortrag vermittelt.
Plasmas as atomization and ionization/excitation sources have been used for more than 50 years. The term plasma spectrochemistry was introduced in the 1980s and is nowadays a topic of annual reviews and different conferences such as the Winter Conference on Plasma Spectrochemistry (held in USA), the European Winter Conference on Plasma Spectrochemistry, and The Nordic conference on Plasma Spectrochemistry.
The development of advanced materials is inherently connected with improvements in analytical chemistry, and often is the driving force for method development in plasma-based spectrometry. Besides the determination of physical characteristics such as tensile strength, density, and conductivity, the investigation of their chemical constituents down to the trace and ultra-trace levels becomes more and more important and, therefore, the demand of sensitive and precise analytical methods is growing. In some cases, the determination of the average content is a sufficient result, for instance for the characterisation of raw material or waste management. However, lately laterally resolved analysis, depth profiling of layered materials and characterization of high purity materials are of growing importance. The aim of this article is to give an introduction into plasma spectrometry and its application in materials science. A theoretical overview of the used plasma techniques and a review on applications with a special focus on direct solid sampling will be presented.