Spectrometers ion mobility

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... 

Principles and Characteristics Ion mobility spectrometry (IMS) is an instrumental technique for the detection and characterisation of organic compounds as vapours at atmospheric pressure. Modern analytical IMS was created at the end of the 1960s from studies on ion-molecule chemistry with mass spectrometers and from ionisation detectors for vapour monitoring. An ion mobility spectrometer (or plasma chromatograph in the original termininology) was first produced in 1970 [272],... 

An ion mobility spectrometer consists of a sample-introduction device a drift tube where ionisation and separation of ions takes place and a detector. Ionisation sources of choice include radioactive sources (e.g. a 63Ni foil), photoionisation methods, corona-spray ionisation, flame ionisation and corona discharge. The most common detection method used to measure the... 

An ion mobility spectrometer offers to prospective users an attractive detector for a GC, from the perspective of detection limits and specificity. A mobility spectrometer, even with low resolution, allows interrogation of compound identities and imparts better specificity than the electron-capture detector. When gaseous analytes are delivered individually to IMS, the mobility spectrum contains information for identification, provided that operating conditions are kept constant for the unknown and reference spectra. The connection of a GC column to an ion mobility spectrometer is... 

Figure l Schematic of pre-concentrator designed to trap particulate matter including traces of explosives on a metal mesh screen. After a sample collection step, the apertures are closed, gas is passed at a low flow rate over the mesh which is resistively heated to 200°C or more, releasing vapors into the gas flow and passed to an analyzer, commonly an ion mobility spectrometer. 

Figure 9 An ion mobility spectrometer called the Quantum Sniffer has an inlet with laser or flash-lamp to warm a surface and a vortex sampler (left frame) to pull sample into the analyzer without contact between analyzer and surface (right frame).

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. 

S.J. Taylor, R.B. Turner and P.D. Arnold, Corona-discharge ionization source for ion-mobility spectrometer, PCT Int. Appl. 1993, 32 pp. CODEN PIXXD2 WO 9311554 A1 19930610... 

C.A. HiU and C.L.P. Thomas, A pulsed corona discharge switchable high resolution ion mobility spectrometer-mass spectrometer, Analyst 128(1) (2003) 55-60. 

M.T. Griffin, J.E. Fulton Jr., R.F. McAtee, R. Gao and L.H. Tsoukalas, Enhanced sensitivity and selectivity in a dual cell ion mobility spectrometer. Proceedings of SPIE-The International Society for Optical Engineering 5085 (Chemical and Biological Sensing IV), (2003) 37-45. 

Construction and characterization of a high-flow, high-resolution ion mobility spectrometer for detection of explosives after personnel portal sampling, Talanta 57(1) (2002) 123-134. 

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. 

R.G. Ewing and CJ. Miller, Detection of volatile vapors emitted from explosives with a handheld ion mobility spectrometer. Field Analytical Chemistry and Technology 5(5) (2001) 215—221. 

R.A. Miller, G.A. Eiceman, E.G. Nazarov and A.T. King, A micro-machined high-field asymmetric waveform-ion mobility spectrometer (FA-IMS), Sensor and Actuators B. Chemical, 67 (2000) 300—306. www.sionex.com (click to products)... 

G.A. Eiceman, E.G. Nazarov, R.A. Miller, E.V. Krylov and A.M. Zapata, Micro-machined planar field asymmetric ion mobility spectrometer as a gas chromatographic detector, Analyst 127(4) (2002) 466-471. 

We have recently explored the use of an ion mobility spectrometer (IMS) for the study of negative ioinnolecule reactions at atmospheric pressure. This instrument, shown in Figure 6, consists of three major components. They are an ion mobility spectrometer, a mass spectrometer, and a gas-handling plant (GHP). 

Figure 6. Diagram of our 1-atm ion mobility spectrometer (IMS) apparatus (a) stainless steel source gas dilution volume, (b) septum inlet, (c) needle valve, (d) Nj source gas supply, (e) source and drift gas exhaust, (f) flow meter, (g) pressure transducer, (h) insulated box, (i) drift tube, (j) ion source, (k) Bradbury-Nielson gate, (I) Faraday plate/MS aperture, (m) drift gas inlet, (n) universal joint, (o) electrostatic lens element, (p) quadrupole mass filter, (q) 6"-diffusion pump, (r) first vacuum envelope, (s) channeltron electron multiplier, (t) second vacuum envelope, (u) 3"-dif-fusion pump, (v) Nj drift gas, (w) leak valve, (x) on/off valves, (y) fused silica capillary, (z) 4-liter stainless steel dilution volume, (aa) Nj gas supply.

Figure 14. A pulsed electron beam ion mobility spectrometer for the study of CPIC over the pressure range of 0.01 to 1.0 atm.

An ion mobility spectrometer,1 like the devices used in most of the sample technologies described in this book, requires ingesting a sample of the medium being searched for explosive molecules. When the medium is water or air, the process is straightforward, but when the sample is to be taken from a solid surface some solvent may be involved. Quantities can be quite small, so papers or cloths, sometimes called swipes are often used. These swipes are normally used dry, but sometimes are solvent saturated, then allowed to dry before sampling. 

TABLE 10.3 Short List of Some manufacturers of Ion Mobility Spectrometers... 

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