MWNTs obtained using iron catalyst and ethylene as a carbon source were submitted to a purification procedure. To purify these materials from amorphous carbon two parallel methods--based on either hydrogen or air treatment--were applied. At the second purification stage iron particles were removed using 1 M or 5 M nitric or hydrochloric acids. The phase composition of the samples was determined using X-ray diffraction method. The sample morphology was characterized using a high resolution transmission electron microscopy. The relative fraction of impurities in the samples was estimated by Raman spectroscopy and the quantitative analysis of metal impurity content was validated by means of thermogravimetric analysis.