Determination of metallic elements in carbon nanotubes by inductively coupled plasma-optical emission spectrometry

When carbon nanotubes (CNTs) are synthesized, some metal elements are usually employed as catalysts. The CNTs synthesized by this method are contaminated with metals and various forms of carbon and other impurities, which in some cases hinders the detailed characterization of such nanotubes and the assessment of their potential utility. Metallic elements (Fe, Cr, Mo, Al and Ni) in CNTs were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). Several sample dissolution procedures were investigated. By using an acid dissolution procedure with a mixture of nitric acid and perchloric, or a fusion procedure with potassium hydrogensulfate, a part of the samples was adsorbed on the wall of a flask or a crucible. However, the CNTs could be completely dissolved after the procedures were repeated several times. When the CNTs were incinerated, a part of molybdenum was sublimated. By a microwave-assisted dissolution procedure, CNTs were completely dissolved with a mixture of nitric acid and perchloric acid. The analytical results of the CNTs obtained by ICP-OES had good reproducibility. The contents of metallic elements in CNTs were drastically reduced when they were purified by acids.