A hemoglobin (Hb) modified glassy carbon electrode consisting of low cost as commercially received impure-multiwalled carbon nanotube (i-MWCNT, 90% purity) and nafion (GCE/i-MWCNT@Hb/Nf) has been demonstrated for improved electric wiring of Hb and efficient direct electron-transfer characteristics. This report is the first attempt for coupling i-MWCNT with Hb for the biosensor purpose. The Hb electrode was assembled by a simple preparation procedure within 38.3 (±2.5) min of time, without any linker, surfactant, promoters, and extensive functionalization of the MWCNT. Impurities within the i-MWCNT such as metal oxides (Fe 3O 4, Co 3O 4, and NiO), graphite, and amorphous carbon were quantitatively identified by X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The metal oxide impurities were found to assist the binding of Hb onto i-MWCNT, whereas the graphitic impurity facilitated the direct electron-transfer reaction. The measured surface excess value of the Hb on the GCE/CNT@Hb/Nf with respect to different CNTs are in the sequences of i-MWCNT > purified-MWCNT > impure single-walled carbon nanotube > functionalized-MWCNT. The GCE/i-MWCNT@Hb/Nf shows enhanced and selective H 2O 2 electrocatalytic reduction signal without interference from cysteine, ascorbic acid, uric acid, nitrite, and nitrate. Note that Hb can mediate the nitrite reduction reaction too; however, no interference has been observed in this work. Various types of milk, cosmetic bleaching cream, and medical real samples were successfully analyzed with recovery values closer to 100%. The electrode has been found to be stable for 110 days. © 2012 American Chemical Society.