Multielement trace determination in SiC powders: assessment of interlaboratory comparisons aimed at the validation and standardization of analytical procedures with direct solid sampling based on ETV ICP OES and DC arc OES |
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Authors: | Ralf Matschat Jürgen Haßler Heike Traub Angelika Dette |
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Institution: | 1. Federal Institute for Materials Research and Testing (BAM), Richard-Willst?tter-Stra?e 11, 12489, Berlin, Germany 2. ESK Ceramics GmbH & Co. KG, Kempten, Germany
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Abstract: | The members of the committee NMP 264 “Chemical analysis of non-oxidic raw and basic materials” of the German Standards Institute
(DIN) have organized two interlaboratory comparisons for multielement determination of trace elements in silicon carbide (SiC)
powders via direct solid sampling methods. One of the interlaboratory comparisons was based on the application of inductively
coupled plasma optical emission spectrometry with electrothermal vaporization (ETV ICP OES), and the other on the application
of optical emission spectrometry with direct current arc (DC arc OES). The interlaboratory comparisons were organized and
performed in the framework of the development of two standards related to “the determination of mass fractions of metallic
impurities in powders and grain sizes of ceramic raw and basic materials” by both methods. SiC powders were used as typical
examples of this category of material. The aim of the interlaboratory comparisons was to determine the repeatability and reproducibility
of both analytical methods to be standardized. This was an important contribution to the practical applicability of both draft
standards. Eight laboratories participated in the interlaboratory comparison with ETV ICP OES and nine in the interlaboratory
comparison with DC arc OES. Ten analytes were investigated by ETV ICP OES and eleven by DC arc OES. Six different SiC powders
were used for the calibration. The mass fractions of their relevant trace elements were determined after wet chemical digestion.
All participants followed the analytical requirements described in the draft standards. In the calculation process, three
of the calibration materials were used successively as analytical samples. This was managed in the following manner: the material
that had just been used as the analytical sample was excluded from the calibration, so the five other materials were used
to establish the calibration plot. The results from the interlaboratory comparisons were summarized and used to determine
the repeatability and the reproducibility (expressed as standard deviations) of both methods. The calculation was carried
out according to the related standard. The results are specified and discussed in this paper, as are the optimized analytical
conditions determined and used by the authors of this paper. For both methods, the repeatability relative standard deviations
were <25%, usually ~10%, and the reproducibility relative standard deviations were <35%, usually ~15%. These results were
regarded as satifactory for both methods intended for rapid analysis of materials for which decomposition is difficult and
time-consuming. Also described are some results from an interlaboratory comparison used to certify one of the materials that
had been previously used for validation in both interlaboratory comparisons. Thirty laboratories (from eight countries) participated
in this interlaboratory comparison for certification. As examples, accepted results are shown from laboratories that used
ETV ICP OES or DC arc OES and had performed calibrations by using solutions or oxides, respectively. The certified mass fractions
of the certified reference materials were also compared with the mass fractions determined in the interlaboratory comparisons
performed within the framework of method standardization. Good agreement was found for most of the analytes. |
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Keywords: | Inductively coupled plasma optical emission spectrometry with electrothermal vaporization (ETV ICP OES) Direct current optical emission spectrometry (DC arc OES) Direct solid sampling technique Silicon carbide powder Method validation Method standardization |
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