ABSTRACT
An ion mobility spectrometer is composed of a central component, the drift tube, where ion formation and characterization occur, and other components that support the measurement made with the drift tube. These other components may be categorized as the utilities, including power supplies, heaters, and gas supply, and the electronics, including detector amplifiers, signal processor, and ion-shutter controller. These are shown in a block diagram for a generalized arrangement in Figure 4-1. The drift tube can be further divided into an ion source, a reaction region, a drift region, and a detector (as shown in Figure 4-2). Although every ion mobility spectrometry (IMS) analyzer will share some or all of the generic design in Figure 4-1, identifying a standard or average IMS instrument is not possible due to the variety of components and designs of drift tubes, the possible configurations for inlets, materials of components, and electronics. Although IMS has been under development for over 30 years as a modern analytical technique, there is little uniformity in analyzer designs, and distinctiveness has actually increased during the past decade with new materials and components, innovations in ion formation and separation, and new commercial analyzers. An exception to this generalization can be found in the instruments produced in large numbers for chemical weapons detection and explosives determinations. In such analyzers, uniformity in construction and performance within a model line is desired, and analyzers are held to defined specifications. Another special feature of commercial analyzers is that the components seen in Figure 4-1 and Figure 4-2 are all integrated into a single package and may not be recognizable as discrete items. In contrast, research-grade instruments can be built from individual components that are available commercially as separate packages, except the ion-shutter controller. This is a specialized electronic unit and is unavailable as a standard item from vendors.
