High-resolution and high-sensitivity MS techniques have enabled the investigation of the chemical composition of both ambient aerosols and clusters. The ionized sample is guided into the MS and undergoes collisions with the background gas in the presence of electric fields. These collisions are far more energetic than any collision that ions are likely to experience in the atmosphere. The collisionally-excited ions can undergo fragmentation, resulting in the detection of only the fragments and not the particles that were initially sampled. The Atmospheric Cluster Dynamics Code (ACDC) is used to model the kinetics of cluster growth, and often, discrepancies in the distribution of clusters predicted by ACDC and those sampled in a mass spectrometer are due to fragmentation.(80; 81) Computational efforts to model the extent of fragmentation a cluster can undergo inside a MS like the APiTOF have shown that clusters undergo fragmentation while moving between the various differentially pumped chambers of the instrument, with highest fragmentation occurring between the first and second chambers. The study also established that the high pressures (7 mTorr -1 Torr) maintained in these chambers also contributed to greater fragmentation. The degree of fragmentation was found to be dependent on the type of clusters, with sulfuric aid-bisulfate clusters losing sulfuric acid molecules and dimethylamine-sulfuric acid clusters exhibiting fragmentation patterns that were highly dependent on the size of the cluster. Typically, larger clusters undergoing fragmentation to a greater extent and via multiple pathways. Extensive fragmentation can skew the interpretation of the results, introducing significant uncertainties in terms of whether the measured/observed results are truly representative of the sampled species. This is an important detail to consider when applying MS to the study of ambient aerosols.