Mobility Spectrometer System

J.E. Parmeter, G.A. Eiceman andJ.E. Rodriguez, Trace Detection of Narcotics Using a Preconcentrator/ Ion Mobility Spectrometer System, NIJ Report 602-00, April 2001. 

K.B. Pfeifer and R.C. Sanchez, Miniaturized ion mobility spectrometer system for explosives and contraband detection. International Journal for Ion Mobility Spectrometry 5(3) (2002) 63—66. 

Discontinuous chemical-detection systems do not provide a signal that is continuous in time, but rather cycle rapidly through a series of phases such as sample collection, preconcentration, separation, and detection in such a way that the overall system is capable of providing a detection report every minute or so. Examples of such systems include ion mobility spectrometers, mass spectrometers, and chromatography-based systems. Many technologies are possible candidates for each of the different phases.2... 

The Block II chemical biological mass spectrometer (CBMS II) is the most recent version in an evolution of fieldable mass spectrometer systems designed for military detection and identification of chemical and biological warfare agents (CWA and BWA, respectively). It builds on the experience and performance of previous versions and employs the latest advances in the components that comprise the system. Two of these predecessors in particular have made important contributions to this development, the mobile mass spectrometer (MM-1) and the Block I chemical biological mass spectrometer (CBMS I). 

At present there are three detection sensor systems in the early development stage. The three candidate detection sensors are, in order of increasing complexity and cost, the continuous electron capture detector (CECD), the ion mobility spectrometer (IMS), and the mass spectrometer (MS). A brief description of these systems follows... 

Figure 4.4 A commercial FUR spectrometer system for near-line, at-line and mobile IR analysis.

Ion mobility spectrometry (IMS) is an instrumental method where sample vapors are ionized and gaseous ions derived from a sample are characterized for speed of movement as a swarm in an electric field [1], The steps for both ion formation and ion characterization occur in most analytical mobility spectrometers at ambient pressure in a purified air atmosphere, and one attraction of this method is the simplicity of instrumentation without vacuum systems as found in mass spectrometers. Another attraction with this method is the chemical information gleaned from an IMS measurement including quantitative information, often with low limits of detection [2 1], and structural information or classification by chemical family [5,6], Much of the value with a mobility spectrometer is the selectivity of response that is associated with gas-phase chemical reactions in air at ambient pressure where substance can be preferentially ionized and detected while matrix interferences can be eliminated or suppressed. In 2004, over 20000 IMS-based analyzers such as those shown in Fig. 1 are placed at airports and other sensitive locations worldwide as commercially available instruments for the determination of explosives at trace concentration [7],... 

Detection - Accepts a sample from the preconcentrator and makes an analysis. Several types of detectors are currently incorporated in trace portals. These detectors include ion mobility spectrometers or mass spectrometers. The detection subsystem needs to be reliable and rugged to perform hundreds to thousands of analyses per day with the necessary sensitivity and specificity required in the trace portal system. Most detectors are concentration-sensitive devices. 

Levin, D.S. Miller, R.A. Nazarov, E.G., Vouros, R, Rapid separation and quantitative analysis of peptides using a new nanoelectrospray-differential mobility spectrometer-mass spectrometer system. Anal. Chem. 2006, 78(15), 5443-5452. 

The efficient transfer of an analyte from its original condition to the ionization region of an ion mobility spectrometer (IMS) is the topic of this chapter. Snccessfnl detection and identification of an analyte by IMS depend on many steps but none more important than those by which a sample is introduced into an instrument. IMS instruments are used for the detection and identification of analytes found in air, water, biological fiuids and tissues, industrial solvents and on surfaces. Because ion mobility spectrometry is such a universal analytical instrument, sample introduction methods are diverse and depend on the type of sample analyzed. Atmospheric pressure operation makes IMS suitable for interfacing with several sample introduction systems as a detector as well as a selective filter for mass spectrometric techniques. 

From Borsdorf, H. Rammler, A. Schulze, D. Boadu, K.O. Feist, B. Weiss, H., Rapid on-site determination of chlorobenzene in water samples using ion mobility spectrometry. Anal. Chim. Acta 2001, 440, 63-70.) (b) Exponential dilution system. (From Sielemann et al.. Detection of alcohols using UV-ion mobility spectrometers. Anal. Chim. Acta 2001, 431, 293-301. With permission.)... 

Barth, S. Baether, W. Zimmermann, S., System design and optimization of a miniaturized ion mobility spectrometer using finite element analysis, IEEE Sensors 2009, 9, 377-382. 

FIGURE 9.11 Schematic of the electrospray ionization, ambient pressure, dual-gate ion mobility, quadrupole ion trap mass spectrometer. This instrument consisted of six primary units an electrospray ionization source, an ion mobility spectrometer, a vacuum interface, ion guides and lenses, a quadrupole ion trap, and a PC-based data acquisition system (not shown). " (Reprinted from Glowers and Hill, Mass analysis of mobility-selected ion populations using dual gate, ion mobility, quadrupole ion-trap mass spectrometry. Anal. Chem. 2005, 77, 5877-5885. With permission.)... 

Tadjimukhamedov, F.K. Jackson, A.U. Nazarov, E.G. Ouyang, Z. Cooks, R.G., Evaluation of a differential mobility spectrometer/miniature mass spectrometer system, J. Am. Soc. Mass Spectrom. 2010, 21, 1477-1481. 

When response to a chemical is strong due to favorable ionization properties of the substance, mobility spectrometers can often provide direct monitoring without effects from potential interferences in the sample matrix. This was seen with the evaluation of nicotine emissions at a production site for transdermal systems (i.e., skin patches) for treating nicotine withdrawal. Nicotine patches are prodnced by depositing drops of nicotine onto an adsorbent layer that is drawn as a continuous... 

Ion mobility spectrometers with hydrated proton ion chemistry is exquisitely sensitive to ammonia, and two teams have sought to engineer IMS-based analyzers for ammonia in water." ° " In the earlier development," ammonia was thermally purged through a silicone membrane, and the limit of detection in this approach was 1.2 mg/L. The membrane was free of memory effects, and pH was controllable and permitted determination of ammonium ion concentrations. The system was engineered to avoid biofouling. 

Limero, T. Brokenshire, J. Cummings, C. Overton, E. Carney, K. Cross, J. Eiceman, G. James, J., A volatile organic analyzer for space station description and evaluation of a gas chromatography/ion mobility spectrometer. International Conference on Environmental Systems 921385, July 1,1992, Seattle, WA. 

Spangler, G.E. Characterization of the ion-sampling pinhole interface for an ion mobility spectrometer/mass spectrometer system. Int. J. Mass Spectrom. 2001, 208, 169-191. 

Ion mobility (IM) mass spectrometers are hybrid instruments that combine an IM separation system with conventional MS systems. An ion mobility spectrometer (IMS) can also serve as a stand-alone ion detection system [72]. An IMS uses gas-phase mobility rather than the m q ratio as a criterion to separate ions [73,74]. The mobility of ions is measured under the influence of an electrical field gradient and cross-flow of a buffer gas, and depends on ion s collision cross section and net charge. 

One recent development that offers scope for direct injection of aqueous samples into an MS system is the high-field, asymmetric waveform ion mobility spectrometer (FAIMS). By interfacing the FAIMS technology to an ESI—MS instrument a significant reduction in detection limits has been achieved for molecules of <300 Da. Preconcentration is unnecessary and analytical times are significantly shortened. Recent appHcations of this technique include naphthenic and haloacetic acids in water and amphetamines, morphine and codeine... 

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