Removal of the residual magnetic metal catalyst from the single-wall carbon nanotubes (SWCNTs) is important prerequisite for many further applications. We present here a facile analysis method enabling direct control of the removed fraction of the catalyst nanoparticles (NPs) after purification. Determination of distribution of the magnetic moments attributed to the catalyst NPs enables proper interpretation of the efficiency and mechanism of the used purification process. The study has been performed on the SWCNTs containing magnetic metal NPs, exposed to sonication and magnetic filtration. Two different SWCNT precursors (HiPco and laser ablation SWCNTs), three solvents and multiple filtration steps, respectively, have been tested. Magnetic property measurements are supported by the results of thermal decomposition and Raman spectroscopy.