Das Polynom dritter Ordnung als Eichkurve der R?ntgenspektrometric

Zusammenfassung Die Methode der quadratischen Optimierung (auch als Methode der kleinsten Quadrate bezeichnet) mit einem Polynomansatz zweiter Ordnung führt zu verschiedenen Eichkurven, je nachdem, ob man die Konzentration als Funktion der Intensität oder die Intensität als Funktion der Konzentration darstellt. Da beide Ansätze mathematisch gleichberechtigt sind, entsteht eine echte Doppeldeutigkeit, die einen systematischen Analysenfehler zur Folge hat.Er wird durch die Anwendung der Interpolationsformel von Newton beseitigt. Da ihre Koeffizienten sehr einfach zu berechnen sind, kann ohne Schwierigkeit mit Polynomen dritter Ordnung gearbeitet werden, die eine bessere Anpassung an die Meßwerte der Standards und damit einen kleineren zufälligen Analysenfehler bewirken.

---

The polynomial of third order as calibration curve in X-ray spectrometry

The method of the least squares with a polynomial of second order leads to different calibration curves depending on the choice of either the concentration as a function of the intensity or the intensity as a function of the concentration. Both statements are mathematically equivalent and an uncertainty of the analysis is therefore caused with a systematical error as a consequence.This uncertainty is removed by the application of Newton's interpolation formula the coefficients of which can be calculated very easily. Therefore it is possible to use a polynomial of third order as calibration function which allows a better accomodation to the measurement results of the standards. Further, the random analytical error is reduced and above all it can be directly calculated.

     

Manuelle Auswertung intermedi?rer Proben in der R?ntgenspektrometrie

Zusammenfassung In einem früheren Aufsatz in dieser Zeitschrift [1] war gezeigt worden, daß sich das Rechenprogramm P 88 auch für die rechnerische Auswertung von Meßergebnissen an intermediären Proben eignet. Als Rechenbeispiel war eine Aluminium-Matrix mit den Analysenelementen Hg, As und Cd verwendet worden. Im vorliegenden Aufsatz werden vier einfache manuelle Methoden am gleichen Beispiel behandelt, wobei über Brutto- und Nettointensitäten mit und ohne Probenwägung ausgewertet wird. Es ergab sich, daß die Auswertung über die Nettointensitäten mit Probenwägung zu den geringsten Analysenfehlern führt.

---

Manual evaluation of intermediate samples in X-Ray spectrometry

The author has shown in a former paper in this journal [1] that the program P 88 is suitable for the evaluation of the measuring results from intermediate samples. As an example for calculation the aluminium matrix with the analyzed elements Hg, As and Cd has been used. In the present paper four simple manual methods of evaluation are treated for the same matrix and elements. The methods are working with gross and net intensities, with and without weighing the samples. The evaluation with net intensities and with weighing the samples resulted in the smallest analysis errors.

     

Der inh?rente Analysenfehler in der R?ntgenspektrometrie

Zusammenfassung Bei der Interelementkorrektur in der Röntgenspektrometrie ist es praktisch zweckmäßig, die Intensitäten anstelle der Konzentrationen der Matrixelemente zu verwenden. Dadurch entsteht ein Analysenfehler. Ein weiterer Fehler ergibt sich dann, wenn nicht alle Elemente der Matrix bekannt sind. Und schließlich besitzt auch die Verteilung der Konzentrationen in Standards und unbekannten Proben einen Einfluß auf das Meßergebnis. Diese Einflüsse lassen sich unter dem Begriff des inhärenten Analysenfehlers zusammenfassen, der meßtechnisch nicht zu erfassen ist. Man kann ihn durch Simulation von Standardproben theoretisch abschätzen. Das Verfahren wird am Beispiel des hochlegierten Stahls und des Erdöls erläutert.

---

The inherent analysis error in X-ray spectrometry

It is suitable to use the intensities instead of the concentrations of the matrix elements when correcting the interelement effects in X-ray spectrometry. Thereby an analysis error arises. If not all elements of the matrix are known, a further error appears. Finally, the distribution of the concentrations in standards and unknown samples has an influence on the analytical result. These influences can all be summarized under the inherent analysis error which cannot be comprehended by measuring techniques but estimated theoretically by simulation of standards and unknown samples. The method is exemplified in the cases of high alloy steel and of mineral oil.

     

Ueber die Genauigkeit jodometrischer Bestimmungen

Ohne Zusammenfassung     

Photoactivity of mechanochemically prepared nanoparticulate titanium dioxide investigated by EPR spectroscopy

Titanium dioxide nanopowders were prepared by mechanochemical synthesis in a high-energy ball mill using TiOSO₄·xH₂O and Na₂CO₃ followed by annealing in the temperature range 200–800 °C. The UVA photonic efficiency of radical processes on synthesized TiO₂ powders was determined by in situ EPR spectroscopy, using, as indicators, the N-oxide spin trapping agents (5,5-dimethyl-1-pyrroline N-oxide and 5-(diisopropoxy-phosphoryl)-5-methyl-1-pyrroline N-oxide) or the radical cation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate, ABTS⁺). The results obtained by monitoring the photoinduced generation of hydroxyl radical spin adducts correlated with those found by the investigation of the photoreduction of ABTS⁺. The presence of iron and chromium ions, which were evidenced in samples milled in steel, decreased the photonic efficiency of radical processes. The presence of a sulfate salt matrix during the annealing process distinctly inhibits the transformation of anatase to rutile. The highest photocatalytic activity was shown by anatase samples which were prepared by milling in corundum and annealed at 700 °C. They were composed of crystallites with a mean size of 25–30 nm and well developed crystal faces.     

Observation of methanol behavior in fuel cells in situ by NMR spectroscopy

The chemical conversion of methanol in direct methanol fuel cells was followed in situ by NMR spectroscopy. Comparing data of the methanol oxidation on Pt and PtRu anode catalysts allowed the role of Ru in both Faradaic and non-Faradaic reactions to be investigated. The spatial distributions of chemicals could also be determined. (Picture: T1-T4=inlet and outlet tubes.).     

Michael Polanyi and the discovery of co‐catalysis: Discussion of an autobiographical letter from Michael Polanyi,FRS to Peter H. Plesch of 17 December 1963

The origin of this memoir was a letter from Michael Polanyi (M. P.) to the present writer (P. H. P.) about their researches in the mid‐1940s into the mechanism of what are now called cationic polymerizations, at the University of Manchester (England). M. P. analyzes his tactics and the mistakes made in directing this research. When the Manchester‐trained researchers made little progress with what was a very recalcitrant problem, M. P. thinking that scientists from a different background might be more sucessful, got P. H. P., from Cambridge, to work with an Oxford‐trained chemist. They recognized that the likely cause of the irreproducibility of these polymerizations was the apparatus used which permitted access of atmospheric moisture to the reaction mixtures containing the moisture‐sensitive catalytic metal halides. Because the only method for following the very fast polymerizations was by monitoring the accompanying temperature rise, and the reactions had to be done below ambient temperature, the reaction vessel needed to be adiabatic, that is a Dewar (Thermos) flask; hence the problem of how to cool its contents. The solution was P. H. P.'s invention of the pseudo‐Dewar vessel, the Dewar space of which, instead of being evacuated permanently, could be filled with air or evacuated. This device permitted the reaction mixture to be made up and cooled, and the reactions to be started without contact with the atmosphere. Thus it was found that isobutene polymerizations, which had stopped unaccountably, could be restarted by water vapor. P. H. P. termed water a “co‐catalyst”. The consequent “Manchester” theory recognized the monohydrate of TiCl₄ as a protonic acid and saw the initiation as due to the protonation of the monomer, with the formation of a tert‐carbenium ion, and these ions, formed repetitively, became the propagating species. The Manchester theory was rapidly accepted because it could also explain observations on other related reactions. The involvement of ions established a link with non‐aqueous electrochemistry. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1537–1546, 2004