Abstract: An IMS system or the like has dopant contained in a way such that it is only released when needed. The dopant could be contained in a device (50) similar to an ink-jet printer and released as droplets (55) when required. Alternatively, the dopant could be trapped in material (156) of a molecular sieve (150) in such a way that it is not normally released into air flowing through the sieve but can be released by energizing a heater (157) in the sieve.

Abstract: An IMS system or the like has dopant contained in a way such that it is only released when needed. The dopant could be contained in a device (50) similar to an ink-jet printer and released as droplets (55) when required. Alternatively, the dopant could be trapped in material (156) of a molecular sieve (150) in such a way that it is not normally released into air flowing through the sieve but can be released by energising a heater (157) in the sieve.

Abstract: An IMS system or the like has dopant contained in a way such that it is only released when needed. The dopant could be contained in a device (50) similar to an ink-jet printer and released as droplets (55) when required. Alternatively, the dopant could be trapped in material (156) of a molecular sieve (150) in such a way that it is not normally released into air flowing through the sieve but can be released by energising a heater (157) in the sieve.

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: An IMS system or the like has dopant contained in a way such that it is only released when needed. The dopant could be contained in a device (50) similar to an ink-jet printer and released as droplets (55) when required. Alternatively, the dopant could be trapped in material (156) of a molecular sieve (150) in such a way that it is not normally released into air flowing through the sieve but can be released by energising a heater (157) in the sieve.

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.

Abstract: An ion mobility spectrometer system includes two cells (1) and (2) driven by a drive unit (12) so that the cells operate at opposite polarities and are switched between different polarities either at regular intervals or in response to detection of a substance in one cell. Two reagents are supplied to both cells (1) and (2), one promoting detection of a substance in the positive mode and the other promoting detection of a substance in the negative mode so that there is no need to switch reagents when the polarity changes.