The elemental analysis and multi-nuclear NMR study of an alkali molten salt used to digest reference and commercial SWCNT powders

For quite some time, alkaline oxidation (or fusion) has been used to solubilize refractory materials and mineral ores. Recently, its application scope was extended to facilitate batch-scale elemental analysis of nanomaterials such as carbon nanotubes. Here, a sodium tetraborate salt was used to digest four different types of single-walled carbon nanotubes. These samples were produced employing Co–Mo or Fe catalyst systems. Their graphitic matrix was exposed to different melt temperatures for a short period of time, following which the concentration of six transition metals was measured. Recoveries in excess of 80% were obtained, with the melt temperature affecting more the elemental extraction in Fe-catalyzed nanotubes. Together with previous results, the work described allows drawing pertinent conclusions on the advantages and limitations of alkaline oxidation as an alternative sample digestion approach for the routine chemical analysis of nanocarbons.