Sample substrates for x-ray microanalysis of particles should be chemically simple and composed of low atomic number elements. Substrates meeting these requirements will generate a minimum number of low energy x-ray peaks that should not interfere with spectra generated by the particles of interest. Elemental carbon fulfills these requirements and carbon planchets are used for the majority of work involving x-ray microanalysis of particles. When particles of interest are carbonaceous, alternate substrates must be sought. Beryllium planchets have traditionally been used for the analysis of carboncontaining particles. However, concerns about beryllium toxicity along with regulations from the Occupational Safety and Health Administration (OSHA) have resulted in diminished use of beryllium as a substrate material. These toxicity issues prompted us to explore the possibility of using elemental boron as a substrate for microanalysis of carbon-containing particles.

Elemental boron is available from chemical supply houses and the material we purchased was in the form of irregularly shaped pieces, approximately 3 cm in the longest dimension.