Abstract: An ion mobility spectrometer has a drift chamber (1) with an inlet (2) at one end by which a gas or vapor being analyzed is supplied to the chamber. After ionization, molecules are admitted through a gate 8 and flow along a drift region (9) to a collector plate (11). A drift gas is flowed through the drift region against the flow of ionized molecules and is circulated along a flow path (31, 32, 40) and (30), which includes a chamber (50) including a dopant. The dopant is 2,4-pentanedione, which has been found to enhance the detection of a number of compounds especially toxic industrial chemicals and nitrogen compounds, such as those present in the breath of mammals.

Abstract: IMS apparatus has a preconcentrator (20) connected at the inlet (2) of an IMS detector (1) such that all gas supplied to the detector flows through the preconcentrator. The preconcentrator comprises a metal tube (21) having a layer of silicone rubber (24) exposed on its inner surface (25). An electrical resistance heating element (22) extends under the silicone rubber layer (24) and is connected to a power source (23) such that the silicone rubber layer can be periodically heated to desorb substances absorbed by the layer and release them to flow to the IMS detector 1 at a higher concentration. The silicone rubber (24) can operate in the desorption phase in the presence of air without degradation.

Abstract: An ion mobility spectrometer has a drift chamber (1) with an inlet (2) at one end by which a gas or vapour being analysed is supplied to the chamber. After ionization, molecules are admitted through a gate 8 and flow along a drift region (9) to a collector plate (11). A drift gas is flowed through the drift region against the flow of ionized molecules and is circulated along a flow path (31, 32, 40) and (30), which includes a chamber (50) including a dopant. The dopant is 2,4-pentanedione, which has been found to enhance the detection of a number of compounds especially toxic industrial chemicals and nitrogen compounds, such as those present in the breath of mammals.