Abstract: A cyclone separator, for the separation of particulate materials from a particle-bearing gas or vapour, in which the particle-bearing gas or vapour is injected into a separating chamber (10), and the particles centrifuged to a separating chamber wall (12) of the separating chamber (10) for collection, the separating chamber wall (12) being wetted by a liquid to assist in collection of the centrifuged particles from the separating chamber wall (12), the separating chamber wall being at least partly porous, the separating chamber wall (12) being wetted by the passage of the liquid through the porous part, to provide a more uniform wetting of the separating chamber wall (12), and hence more efficient particulate collection than previously achieved by prior art methods. The cyclone separator of the invention may also be used for the separation and collection of gas or vapour-borne vapours, in place of particulates.

Abstract: A fluid sampling system has a drift cell (60) enclosing a first fluid. An inlet chamber (62) communicates with the body of first fluid via an orifice (74). A series of negative pressure pulses is applied to the first fluid, causing a sample of a second fluid to be drawn in through the orifice (74). The sample is then entrained into the air flow of a closed loop circulatory system and is detected or measured by an ion mobility spectrometer. A second chamber may be linked to the first chamber, with the negative pressure pulses provided by the second chamber.

Abstract: An ion mobility spectrometer comprises an ion mobility cell (10) into which molecules of a sample to be analysed are introduced. The ion mobility cell (10) is doped with ions produced by a corona discharge ionisation source (40). In one mode of operation, the corona discharge ionisation source (40) operates to produce a continual dopant stream, and in a second mode of operation, the corona discharge ionisation source (40) produces dopant ions selectively. In the non-continuous mode of operation, the ion mobility cell (10) may be doped with chemical dopant ions instead, switching between the two dopant regimes being accomplished very rapidly. The ion mobility spectrometer is particularly suitable for the detection of explosive compounds and narcotics, the ion mobility spectrum of explosives doped with ions from the corona discharge ionisation source differing from the ion mobility spectrum of such explosive compounds doped with chemical dopants.

Abstract: A fluid sampling system has a fluid enclosing element, such as drift cell (60), enclosing a volume of a first fluid. A body of a second fluid, for example in an inlet chamber (62), communicates with the body of first fluid via a small orifice (74). A series of negative pressure pulses is applied to the first fluid by an electromechanical transducer (92), each negative pulse causing a sample of the second fluid to be drawn in through the orifice (74). The sample is then entrained into the air flow of a closed loop circulatory system, and can be detected or measured by any appropriate equipment such as an ion mobility spectrometer.

Abstract: A drift chamber for an ion mobility spectrometer includes an array of conductive electrodes (12, 14, 16, 18) mounted upon a common insulating substrate (10) such as a printed circuit board. The printed circuit board may also form one side of a rectangular enclosure (24), thus allowing the drift chamber to be substantially smaller than previously. The printed circuit board may have a track (60) around its periphery to which the rectangular enclosure (24) can be attached, thus creating a gas-tight seal.

Abstract: An ion mobility spectrometer includes a spectrometer housing (10) and, within the housing, an ion mobility spectrometer cell (12), a volume of vapour absorbent material (30), and a fan (38) for inducing a flow of recirculating cleaning air through the cell (12) and the absorbent material (30). The vapour absorbent material is held in close proximity with the cell, providing the possibility of constructing a miniature instrument without the need for any external air supply.

Abstract: In the type of ion mobility spectrometer having a unidirectional drift and source flow (30) which is exhausted (22) downstream of an ionisation source (10), improved sensitivity is obtained by entraining the effluent (18) from a gas chromatograph within a faster moving further gas flow (32), both being introduced in a direction counter to that of the said unidirectional flow.

Abstract: Ion Mobility Spectrometry (IMS) equipment comprises an enclosed compartment (10) contained within which there is an IMS cell (12) and a body of absorbent material (14). Samples for detection by the cell (12) are introduced into the compartment (10) by means of a pinhole (30), the samples being drawn in by a negative pressure pulse within the compartment produced by means of a loudspeaker (40). A sample, once it has been drawn in and detected by the cell (12), will diffuse within the compartment (10) and any water vapour or other interfering species thus introduced will be absorbed by the absorbent material (14) so maintaining a clean, dry atmosphere within the device.

Abstract: There is disclosed an ion mobility detector having a sample inlet membrane means for flowing a sample passing through the membrane over an ionisation source to an ion reaction region, with which two or more ion drift regions communicate, means for impressing a potential gradient on each drift region, an ion injection shutter at the entrance to each drift region whereby the drift region can be made accessible or inaccessible to ions of a particular sign located in the reaction region, an ion detector in each drift region, means for passing drift gas down each drift region to the reaction region and exit means in the reaction region remote from the ionisation source for venting drift gas from the reaction region, the ionisation source (26) being offset from the reaction region (27).