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Nichts wissen macht nichts? Erfahrungen mit dem "Standardlosen" Analyseprogramm IQ+.
Die moderne semiquantitative Röntgenfluoreszensanalyse bietet als feststoffanalytisches Verfahren die Möglichkeit, chem. Elemente einer völlig unbekannten Probe schnell und zerstörungsfrei qualitativ und quantitativ zu bestimmen. Im Gegensatz zur konventionellen Kalibration, die sich auf eine Elementauswahl beschränkt, wird bei der semiquantitativen RFA das gesamte mögliche Elementspektrum (5?Z?92, B-U) erfasst.
Nach einem Scan, der sich in anregungs- und erfassungsoptimierte Teilscans aufteilt, werden aus den Peaklagen zunächst die Elemente erkannt. Aus den Peakhöhen werden dann, über iterativ arbeitende Fundamentalparameter gestützte Rechenprogramme, die Elemente quantitativ bestimmt. Die gebräuchlichen semiquantitativen Programme basieren auf Universalkalibrationen wobei die Probenart (Metall, Glas, Pressling
) nicht berücksichtigt wird.
In der BAM wurde nun begonnen, probenspezifische Kalibrationen zu erstellen, so dass die Richtigkeit des Analyseergebnisses gesteigert werden konnte.
Ziel ist es, einen großen Teil der analytischen Fragestellungen an ständig wechselnd zusammengesetzten Proben feststoffanalytisch mit der RFA bearbeitbar zu machen.
Einsatz der RFA bei der Zertifizierung von Referenzmaterialien
Der Bedarf an Referenzmaterialien für die chem. Analytik steigt stetig. Nur durch Einsatz moderner Analysenmethoden kann die Nachfrage gedeckt werden.
Die RFA als hochpräzises Verfahren, ist aufgrund der sehr geringen Verfahrensstreuung in der Lage, bei der Beurteilung der Homogenität des Kanditatenmaterials entscheidene Informationen über die Analytverteilung zu liefern.
Zur Zertifizierung von Referenzmaterial wird in der anorg. chem. Analytik häufig die ICP-OES eingesetzt.
Die RFA, in Kombination mit der Rekonstitutions- und Boratschmelztechnik, ist bei der Zertifizierung eine Analysenmethode, die sich in Bezug auf Probenvorbereitung und Messmethodik grundsätzlich von der ICP-OES unterscheidet.
Dadurch trägt sie zur analytischen Methodenvielfalt und damit zur Richtigkeit des zertifizierten Wertes bei und erfüllt zudem im vollsten Maße die Anforderung an metrologischer Rückführbarkeit.
Phosphorus (P) is an essential element for all living organisms and cannot be replaced. Municipal sewage sludge is a carrier of phosphorus, but also contains organic pollutants and heavy metals. A two-step thermal treatment is suggested, including mono-incineration of sewage sludge and subsequent thermochemical treatment of the ashes. Organic pollutants are completely destroyed by mono-incineration. The resulting sewage sludge ashes contain P, but also heavy metals. P in the ashes exhibits low bioavailability, a disadvantage in farming. Therefore, in a second thermochemical step, P is transferred into mineral phases available for plants, and heavy metals are removed as well. The thermochemical treatment was investigated in a laboratory-scale rotary furnace by treating seven different sewage sludge ashes under systematic variation of operational parameters. Heavy metal removal and the increase of the P-bioavailability were the focus of the investigation. The present experimental study shows that these objectives have been achieved with the proposed process. The P-bioavailability was significantly increased due to the formation of new mineral phases such as chlorapatite, farringtonite and stanfieldite during thermochemical treatment.
Certification of the mass fractions of Pt, Pd and Rh in a used car catalyst reference material
(2009)
The high economic value of catalysts containing the platinum group elements platinum, rhodium and palladium as active components causes the need to be able to measure the precious metal loading with small uncertainty and to have suitable certified reference materials fulfilling high demands on the quality of the certified values. In European Reference Material ERM®-EB504, a used cordierite-based car catalyst material, mass fractions of platinum, palladium and rhodium were certified. The raw material was milled, homogenised and annealed before analysis. Seventeen laboratories experienced in precious metals analysis participated in the certification interlaboratory comparison, most of them analysing with inductively coupled plasma optical emission spectrometry using different sample pretreatment techniques. Homogeneity testing was carried out using X-ray fluorescence spectrometry. The certified mass fractions of Pt, Pd and Rh and their expanded uncertainties (k = 2) in ERM®-EB504 are (1777 ± 15), (279 ± 6) and (338 ± 4) mg/kg respectively.
The sequence of reactions accompanying the thermochemical treatment of an iron- and aluminium-bearing sewage sludge ash was ascertained by investigating two systematic series of samples. The ash was thermochemically treated in a lab-scale rotary furnace after mixing it with a chlorine-donor, either CaCl2 or MgCl2. Within each of these two sample series only a single process parameter, the reaction temperature, was varied, namely between 350 and 1050°C. It was found, that among the numerous crystalline phases present in the raw ash only quartz and hematite continue to exist after thermochemical treatments carried out at 1050°C, whereas all other components undergo at least one decomposition-recrystallization cycle. Some of the components re-crystallize even several times. It was proved that the restructuring of the calcium- and phosphorus-bearing mineral phases proceeds via the formation of chlorspodioside, Ca2PO4Cl. The influence of the type of chlorine-donor on the final product was elucidated in detail and - to the best of our knowledge - for the first time crystalline AlPO4 was found in a sewage sludge ash and its decomposition was investigated, too.
In this study the microscopic homogeneity of the newly developed plastic reference materials BAM H001-BAM H010 was investigated. The materials consist of an acrylonitryle-butadien-styrene terpolymer, doped with different amounts of the elements Br, Cd, Cr, Hg and Pb. For the quantitative determination of the degree of homogeneity, a procedure proposed by Kempenaers et al. (Fresenius J. Anal. Chem., 2001, 369, 733-737) was used. On every sample an extensive number of different points were analyzed and standard deviation for every element mentioned above was used to calculate a minimal sampling mass that is necessary to reach a certain level of uncertainty caused by inhomogeneity (mmin,5%). The experiments were taken out with synchrotron µ-XRF (SR µ-XRF) at BESSYII in Berlin and by laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS). The calculated values for mmin,5% of both techniques showed comparable results for all elements. It could be shown that the materials are suitable for calibration of micro analytic techniques if at least 64 µg are used.
For the first time evidence is provided that a nanocrystalline and stacking-disordered, chemically stabilized β-cristobalite form of AlPO4 occurs in a sewage sludge ash (SSA). This proof is based on a combined X-ray powder diffraction and X-ray fluorescence investigation of an SSA produced at a large-scale fluidized bed incineration facility serving a catching area with a population of 2 million. The structural and chemical characterization was carried out on 'as received' SSA samples as well as on solid residues remaining after leaching this SSA in sodium hydroxide solution. Thus, it was ascertained that the observed nanocrystalline and stacking-disordered cristobalite-like component belongs to the aluminum phosphate component of this SSA, rather than to its silicon dioxide component. In addition, a direct proof is presented that the chemically stabilized β-cristobalite form of AlPO4 does crystallize from X-ray amorphous precursors under conditions that mimic the huge heating rate and short retention time (just seconds at T ≈ 850°C), typical for fluidized bed incinerators.