Determination of trace metals in industrial boron carbide by solid sampling optical emission spectrometry. Optimization of DC arc excitation (current, atmosphere and chemical modifier)

Autor: Otto Förster, Jürgen Hassler, Tibor Kántor
Rok vydání: 2006
Předmět:
Zdroj: Microchimica Acta. 156:231-243
ISSN: 1436-5073
0026-3672
Popis: Graphite arc emission spectrometry has become possible as a result of the invention of novel types of optical spectrometers with Echelle-optics and semiconductor array detectors, and by the application of electronically controlled, high current arc generators. An optimization of the excitation parameters to boron carbide analysis is reported here, measuring background corrected line intensities that were integrated for the time of total evaporation of 5 mg boron carbide sample with or without added chemical modifiers. The following set of experimental conditions were compared with respect of analytical sensitivity and precision: (A) no modifier, Ar + O2 (20%), 16 A; (B) sample + graphite powder (1 + 1), Ar + O2 (20%), 16 A; (C) sample + CaF2 (1 + 1), Ar, 25 A; (D) sample + CaF2 + graphite powder (1 + 1 + 1), Ar, 25 A. The graphite powder modifier resulted in improved precision in general, and the CaF2 was effective as a plasma ionization buffer and fluorinating agent. The best compromise was found under conditions B, when oxygen was present in the discharge atmosphere. This is likely due to the stepwise conversion of the boron carbide matrix to the more volatile boron oxide. Under conditions B, detection limits in the ranges of 0.3–9 µg g−1 for Al, Ca, Cr, Cu, Fe, Mg, Mn and Si and that of 18–38 µg g−1 for Ti, W, and Zr were attained. Average RSDs of 10.2 and 9.7% were found, respectively, without and with internal referencing to boron.
Databáze: OpenAIRE
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