A detailed analysis of TUBALL single‐walled carbon nanotubes (SWCNTs) after two‐step purification involving acid purification treatment with concentrated HCl, HNO3, H2SO4 and solution of HNO3:H2SO4 followed by magnetic processing is presented. The purity degree from iron higher than 99% is achieved, and the yield obtained by the above process is about 75 wt.%. Such high purity of the resultant sample is achieved by removing of the external iron nanoparticles by acid treatment and following extraction of nanotubes containing encapsulated nanoparticles under applied magnetic field. A comprehensive characterization of SWCNTs by Raman, optical absorption, and X‐ray photoelectron spectroscopies reveals purification‐induced changes in the integrity, composition, and electronic properties of SWCNT.