A measuring apparatus (200) comprises: - an input (201) to receive an aerosol sample (FG1), - a modifier unit (100) to provide a modified sample (MG1) by removing particles (P1) of the aerosol sample (FG1), and - a sensor unit (SEN1) to measure a spectral profile (PRF) by detecting molecules (VOC1) of the gas phase of the modified sample (MG1), wherein the spectral profile (PRF) is a mobility spectrum or a mass spectrometer spectrum, the modifier unit (100) is arranged to generate a corona discharge (DSR1), to form charged particles (P2) by charging particles (P1) of the aerosol sample (FG1) with the corona discharge (DSR1), and to provide the modified sample (MG1) by removing the charged particles (P2) with an electric field (EF1), the particle removal efficiency (EFF(d)) of the modifier unit (100) has a cutoff size (dCUT) to prevent propagation of particles larger than the cutoff size (dCUT) to the sensor unit (SEN1), and the cutoff size (dCUT) is in the range of 1 nm to 20 nm.