Single-wall carbon nanotube (SVVNT) samples grown by the CoMoCAT method are investigated by resonance Raman scattering and optical absorption. The environment effects in the population of the different (n,m) nanotubes present in the samples are characterized for DNA-wrapped nanotubes and the results are compared with SDS-wrapped CoMoCAT nanotubes. A significant decrease in the Raman intensity of metallic nanotubes is observed in the DNA-wrapped sample as compared to the SDS-wrapped sample, supporting the DNA-based separation method. This result is confirmed by optical absorption measurements in both samples. (C) 2007 Elsevier B.V. All rights reserved.