Particularly the mid-infrared spectral regime offers the possibilities to analyze characteristic spectral signatures of materials, which allow to identify the chemical composition of specimens. Near-field imaging of a mixture consisting of cylindrical tabacco mosaic viruses (TMV) and poly (methyl methacrylate) (PMMA) nanobeads at frequencies between 1550 and 1800cm^-1 allows to identify individual particles on the basis of their near-field spectral signature. The recorded near-field spectra show that the near-field resonance for TMV is centered around 1650cm^-1, whereas the resonance of PMMA can be found in the spectral range around 1730cm^-1. Possible applications range from the analysis of chemical composition or structural analysis (molecular conformation) of single proteins or protein subunits to the characterization of other organic as well as inorganic nanoparticles.