The presence of metallic nanoparticles (NPs) in aerosols has raised concern about their fate in the environment through natural processes and anthropological activities. The state-of-the-art technologies for direct aerosol characterization cannot reach real-time measurement or the signal of metallic particle signal cannot be separated from other components. In the last decade, single particle inductively coupled plasma mass spectrometry (spICP-MS) has been developed to obtain simultaneously the particle size distribution (PSD), particle number concentration (PNC), and elemental composition of nanoparticles in liquid and solid samples. However, this technology has not been applied for direct aerosol characterization due to several limitations which need gas conversion, online dilution, and pressure stabilizer requirements. For this purpose, in this thesis, new online methods have been developed for the real-time characterization of metallic NPs in aerosols. Firstly, a hyphenated setup consisting of a rotating disk diluter which was coupled to spICP-MS (RDD-spICP-MS) has been built up and validated for argon and air atmospheres. Here RDD works as an online dilution and/or a gas convertor. Xe has been used as an internal standard for the calibration in different atmospheres. The setup was evaluated for its ability to monitor metallic NPs if mixed with a matrix of different sizes of NPs, e.g. metal salts, inhalable particle matters, and road dusts. Secondly, fractionation instruments including differential mobility analyzer (DMA) and centrifugal particle mass analyzer (CPMA) were coupled to RDD-spICP-MS. A comparison study between online fractionation (DMA and CPMA) and online dilution (RDD) for separating the metallic NP signal from the metal salts was performed. The results indicate that the separation performance was in the following order: DMA>RDD>CPMA. Lastly, the setup was applied to monitor the propagation of NPs after detonation of metal azide. In conclusion, the work performed in this PhD thesis demonstrated that real-time metal aerosol particle characterization performance can be improved by coupling conventional ICP-MS or spICP-MS technology with advanced sampling, dilution, and fractionation systems. The work also paves the way for new applications in nanoparticle synthesis technology where the monitoring of the formation of metallic particles is essential.