MS versus IMS
Figure 1 is a starting point for comparing MS and IMS detectors. Both MS and IMS use an ionization method to differentiate compounds. IMS uses a radioactive 63Ni source to create a plasma of ions and charges to ionize neutral molecules. In this step IMS must also use a dopant reagent. The Syagen MS detector uses a safe, non-radioactive ionization method and does not require the use of consumable dopant, like IMS. Once the compounds are ionized they are then measured in a drift tube analyzer. IMS operates at atmospheric pressure, which creates two problems: (1) the ionized molecules can interact with other molecules and lose their charge (charge or ion suppression) and (2) the ions that enter the IMS analyzer broaden out in their transit causing a serious loss of resolving power and detection accuracy
In contrast the Syagen MS detector uses a low pressure ionizer that does not lead to ion suppression and a Time of Flight analyzer operated under vacuum conditions, so there is no loss of resolving power and detection accuracy. The net effect is that MS has 10-100 times better resolving power than IMS, which translates to much greater detection accuracy, lower false positive rates, and the capability to screen for a much greater number of explosives compounds. Figure 1 shows why resolving power is important. With high MS resolution it is very easy to distinguish target compounds (shown in red) from background compounds (shown in black). This is clearly not true for IMS.