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Fire Retardancy of Polymers
(2003)
Red Phosphorus, Nanocomposites and Intumescence Catings - Three Examples of Advanced Fire Retardancy
(2003)
Multielement trace determination in high purity advanced ceramics and in high purity metals
Ralf Matschat, Hans-Joachim Heinrich, Michael Czerwensky, Sandra Kuxenko and
Heinrich Kipphardt
Federal Institute for Materials Research and Testing (BAM),
Richard-Willstaetter-Strasse 11, D-12489 Berlin, Germany
Certified reference materials (CRMs) are of high importance to check the trueness of results in chemical analysis. In the field of advanced ceramics two CRMs were developed in the last years by the Federal Institute for Materials Research and Testing - (BAM), one for silicon nitride and one for silicon carbide. The certification of these materials is briefly discussed in this contribution. Both CRMs are not of extremely high purity in the classical sense, but besides their application by industry they are appropriate to be used for the validation of special methods used for trace determination in accordant high purity materials. This is demonstrated for the example of ultrapure silicon carbide which was analyzed by solid sampling electrothermal atomic absorption spectrometry (SS ET AAS). Wet chemical dissolution of this pure material typically introduces blanks which are too high for ultratrace analysis. Therefore SS ET AAS as a direct method was applied which does not need any wet chemical sample preparation. This method can be applied very effectively concerning sample throughput. But, as for all direct solid sampling methods, the calibration is a problem difficult to solve. By using the accordant CRM it could be demonstrated, that the calibration with liquid sample aliquots can be performed without affecting the trueness of the results. The analytical parameters and the performance of the method are discussed.
Besides the so-called matrix CRMs, as reported for silicon nitride and silicon carbide, BAM is also certifying primary pure reference materials used as the National Standards for inorganic analysis in Germany. This work is performed in the frame of an extensive project in co?operation with the sister institute of BAM, the Physikalisch Technische Bundesanstalt (PTB). The crucial point of this project is the certification of the purity of high purity materials, each representing one element of the periodic table. Up to now more than ten primary CRMs are certified or not far from being certified. A variety of different analytical methods was necessary to determine the trace contents of metallic and non-metallic impurities from almost the whole periodic table in the high purity materials. Using high purity copper as an example the application and the results of the different methods applied are demonstrated. Another example presented is high purity iron. In this context the very good comparability of the results from two different methods, used for the determination of metallic traces is demonstrated. One of these methods was the "working horse" - the sector field high resolution ICP mass spectrometry (HR ICP-MS) mainly used in low resolution mode to exploit the good detection power and the other one was the electrothermal atomic absorption spectrometry (ET AAS), which was used to confirm the results of the HR ICP-MS. The analysis of pure molybdenum is presented as a third example. The problems of spectral matrix interference are discussed and different ways of their handling are pointed out. By this example it can also be demonstrated, how the coating of the inlet cones of the ICP mass spectrometer by matrix elements of solutions - which normally is an adverse effect - can be advantageously used to decrease the measured blank values of some analyte elements drastically.