| A novel atmospheric pressure ion mobility orthogonal reflector time-of-flight mass spectrometer (IM(tof)MS) that routinely achieves mobility and mass separation efficiencies in line with theoretical limits has been successfully constructed. The current instrumental set up, using only modest settings, achieved over 133,000 theoretical plates (at a resolving power of 155 for APIMS and 1200 for TOFMS) for a singly charged G/V-type chemical warfare agent (CWA) nerve simulant (dimethyl methylphosphonate (DMMP)) in less than 12 msec. Moreover, the use of several theoretical models (rigid-sphere, polarization-limit, 12-6-4, and 12-4 potential models) to estimate the gas-phase collision cross-sections of the Chapman-Enskog theory for predicting the mobility of alkyl amines was explored. It was found that the modified 12-4 potential that compensates for the center of charge not being at the same location as the centers of mass showed improved agreement over the other collision cross-section models with respect to experimental data. It was also noted that departing ions from the APIMS drift tube could be selectively fragmented (collision-induced dissociations) by increasing the accelerating field in the pressure interface region that bridged the APIMS to the TOFMS. |
