For example, Jarrold and co-workers have used charge-detection mass spectrometry in a modified cone trap to study proteins and nanoparticles such as viruses or components thereof, as discussed in a recent review. The Williams group has also applied charge detection mass spectrometry to study megadalton (MDa) particles, for example, reporting experiments aimed at rapid particle sizing and study of ion emission from salt nanoparticles. A related approach is ion-cyclotron resonance mass spectrometry, which, for example, has been used by the Marshall group to study char particles. In these experiments, NP detection was done by monitoring the weak signals resulting from inductive or capacitive interactions when highly charged particles pass through or near pickup electrodes, and the signal amplitudes also give the Q values, thus allowing M to be extracted from M/Q measurements.