Abstract: An ion mobility spectrometer (100) comprising a first ion source (102-1, 108-1) for providing positive ions to be analyzed, an electric field applier arranged to provide an electric field configured to move the positive ions in a first direction towards a first ion detector (106-1, 110-1) adapted for detecting the positive ions, and a second ion source (102-2, 108-2) for providing negative ions to be analyzed, wherein the electric field applier is arranged to move the negative ions in a direction opposite to the first direction, towards the first ion source (102-1, 108-1) and towards a second ion detector (106-1, 110-1) adapted for detecting the negative ions.

Abstract: An ion mobility spectrometer (100) comprising a first ion source (102-1, 108-1) for providing positive ions to be analysed, an electric field applier arranged to provide an electric field configured to move the positive ions in a first direction towards a first ion detector (106-1, 110-1) adapted for detecting the positive ions, and a second ion source (102-2, 108-2) for providing negative ions to be analysed, wherein the electric field applier is arranged to move the negative ions in a direction opposite to the first direction, towards the first ion source (102-1, 108-1) and towards a second ion detector (106-1, 110-1) adapted for detecting the negative ions.

Abstract: An ion mobility spectrometer has a pair of electrodes and midway along the drill chamber. A high field is applied between the electrodes and sufficient to modify ions in the region of the electrodes such that they move at a different rate towards the collector plate. This is used to modify the time of flight of selected ions or ion clusters and enable identification of ambiguous peaks on the IMS spectrum.

Abstract: A field asymmetric ion mobility spectrometer (FAIMS) has an analyte ion source assembly by which an analyte substance is ionized and supplied to the inlet of the spectrometer. The ion source assembly has an upstream source of clean, dry air and two ion sources of opposite polarity arranged at the same distance along the flow path. The ion sources are arranged so that the overall charge of the plasma produced is substantially neutral. The analyte substance is admitted via an inlet downstream of the ion sources and flows into a reaction region of enlarged cross section to slow the flow and increase the time for which the analyte molecules are exposed to the plasma.

Abstract: An ion mobility spectrometer has several electrodes spaced along its ion source region. Voltages are applied to the electrodes to produce a voltage gradient along the length of the ion source region. By varying the voltage gradient, the residence time of ions in the ion source region can be selectively varied. Typically, the spectrometer is arranged to reduce the residence time in response to a decrease in the amplitude of an ion peak detected at the far end of the drift region.

Abstract: An ion mobility spectrometer has several electrodes spaced along its ion source region. Voltages are applied to the electrodes to produce a voltage gradient along the length of the ion source region. By varying the voltage gradient, the residence time of ions in the ion source region can be selectively varied. Typically, the spectrometer is arranged to reduce the residence time in response to a decrease in the amplitude of an ion peak detected at the far end of the drift region.

Abstract: An ion mobility spectrometer has a pair of electrodes and midway along the drift chamber. A high field is applied between the electrodes and sufficient to modify ions in the region of thee electrodes such that they move at a different rate towards the collector plate. This is used to modify the time of flight of selected ions or ion clusters and enable identification of ambiguous peaks on the IMS spectrum.

Abstract: An ion mobility spectrometer has several electrodes spaced along its ion source region. Voltages are applied to the electrodes to produce a voltage gradient along the length of the ion source region. By varying the voltage gradient, the residence time of ions in the ion source region can be selectively varied. Typically, the spectrometer is arranged to reduce the residence time in response to a decrease in the amplitude, of an ion peak detected at the far end of the drift region.

Abstract: A field asymmetric ion mobility spectrometer (FAIMS) has an analyte ion source assembly by which an analyte substance is ionized and supplied to the inlet of the spectrometer. The ion source assembly has an upstream source of clean, dry air and two ion sources of opposite polarity arranged at the same distance along the flow path. The ion sources are arranged so that the overall charge of the plasma produced is substantially neutral. The analyte substance is admitted via an inlet downstream of the ion sources and flows into a reaction region of enlarged cross section to slow the flow and increase the time for which the analyte molecules are exposed to the plasma.

Abstract: An ion mobility spectrometer has several electrodes spaced along its ion source region. Voltages are applied to the electrodes to produce a voltage gradient along the length of the ion source region. By varying the voltage gradient, the residence time of ions in the ion source region can be selectively varied. Typically, the spectrometer is arranged to reduce the residence time in response to a decrease in the amplitude, of an ion peak detected at the far end of the drift region.

Abstract: A field asymmetric ion mobility spectrometer (FAIMS) has an analyte ion source assembly by which an analyte substance is ionized and supplied to the inlet of the spectrometer. The ion source assembly has an upstream source of clean, dry air and two ion sources of opposite polarity arranged at the same distance along the flow path. The ion sources are arranged so that the overall charge of the plasma produced is substantially neutral. The analyte substance is admitted via an inlet downstream of the ion sources and flows into a reaction region of enlarged cross section to slow the flow and increase the time for which the analyte molecules are exposed to the plasma.

Abstract: An ion mobility spectrometer has several electrodes spaced along its ion source region. Voltages are applied to the electrodes to produce a voltage gradient along the length of the ion source region. By varying the voltage gradient, the residence time of ions in the ion source region can be selectively varied. Typically, the spectrometer is arranged to reduce the residence time in response to a decrease in the amplitude, of an ion peak detected at the far end of the drift region.

Abstract: An ion mobility spectrometer has a pair of electrodes and midway along the drift chamber. A high field is applied between the electrodes and sufficient to modify ions in the region of thee electrodes such that they move at a different rate towards the collector plate. This is used to modify the time of flight of selected ions or ion clusters and enable identification of ambiguous peaks on the IMS spectrum.

Abstract: An ion mobility spectrometer has a pair of electrodes (13A) and (13B) midway along the drift chamber (7). A high field is applied between the electrodes (13A) and (13B) sufficient to modify (e.g. fragment) ions in the region of the electrodes such that they move at a different rate towards the collector plate (8) . This is used to modify the time of flight of selected ions or ion clusters and enable identification of ambiguous peaks on the IMS spectrum.

Abstract: A FAIMS ion mobility spectrometer is arranged so that the analyte is subject to different ion chemistries at different locations along the spectrometer. Different dopants, or different concentrations of dopants or water vapor are admitted at various locations, such as at the inlet, between the inlet and the ionizer between the ionizer and the gate, between the gate and the FAIMS parallel plates, through an opening in one of the plates, or between the end of the plates and the detector.

Abstract: A field asymmetric ion mobility spectrometer (FAIMS) has an analyte ion source assembly by which an analyte substance is ionized and supplied to the inlet of the spectrometer. The ion source assembly has an upstream source of clean, dry air and two ion sources of opposite polarity arranged at the same distance along the flow path. The ion sources are arranged so that the overall charge of the plasma produced is substantially neutral. The analyte substance is admitted via an inlet downstream of the ion sources and flows into a reaction region of enlarged cross section to slow the flow and increase the time for which the analyte molecules are exposed to the plasma.

Abstract: An ion mobility spectrometer has several electrodes spaced along its ion source region. Voltages are applied to the electrodes to produce a voltage gradient along the length of the ion source region. By varying the voltage gradient, the residence time of ions in the ion source region can be selectively varied. Typically, the spectrometer is arranged to reduce the residence time in response to a decrease in the amplitude, of an ion peak detected at the far end of the drift region.

Abstract: An ion mobility spectrometer has an inlet opening into an ionization region including a conventional ionization source. A series of several charged, circular electrode plates with aligned apertures extending therethrough provides a drift region on the opposite side of the ionization region from the inlet. A gas inlet connected to a source of clean, dry flushing gas opens between the ends of the drift region, with the gas flowing against the ion flow to one side to remove water molecules from the analyte. Gas flowing in the opposite direction is effective to help drive the dry analyte ions to an analysis region provided by two parallel asymmetric field plates.

Abstract: Detection apparatus including an IMS detector (1, 100) or the like has a gas inlet (10) with a gas flow path arrangement (40, 41, 102) by which sample gas is supplied to the detector. In one arrangement two regions (40 and 41) of a gas flow path arrangement are connected in parallel. The regions are provided by respective GC capillary tubing coils (40) and (41) coated internally with materials of different absorption characteristics so that the time taken for the chemical of interest to reach the detector (1) is different along the two coils, thereby giving responses in the detector at different times. Alternatively, two regions of a gas flow path could be provided by regions (104 and 106) arranged serially one after the other.

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.