Figure 7.

Timeline in development of Mini-MS. In the 1990s, microelectromechanical systems (MEMS) were used in miniaturized mass spectrometers for the fabrication of compartments (e.g., analyzers and vacuum pump). Advancements have been made expanding development of miniaturized analyzers to include quadrupole mass filter, sector, time-of-flight (TOF), and ion trap. Figure reproduced with permission from Reference 117. Ion trap is currently the most common analyze due to qualities like high-pressure tolerance, ease of miniaturizing, and MS/MS capability. Therefore, the evolution of ion trap mass analyzers is described, which changed geometry from 3D hyperbolic quadrupole to 2D toroidal, 3D cylindrical, to 2D rectilinear, and finally to 2D halo ion trap. Figures reproduced with permission from Reference 133, 134 and 136. The Mini-series (Purdue University, West Lafayette) are well-known examples of the ion-trap mini-MS system. Figure reproduced with permission from Reference 141. Besides ion trap evolution, continuous developments are being observed for other analyzers. These include chip-based quadrupole coupled to HPLC (Microsaic 3500 MiD, Microsaic Systems) and recently triple quadrupole mini-MS is invented which enables MS/MS. Figure reproduced with permission from Reference 122 and Reference 126.