Abstract: Time-of-flight mass spectrometer comprising a first drift region and a second drift region enclosed within an evacuation chamber; a means of introducing an analyte of interest into the first drift region; a pulsed ionization source which produces molecular ions from said analyte of interest; a first foil positioned between the first drift region and the second drift region, which dissociates said molecular ions into constituent atomic ions and emits secondary electrons; an electrode which produces secondary electrons upon contact with a constituent atomic ion in second drift region; a stop detector comprising a first ion detection region and a second ion detection region; and a timing means connected to the pulsed ionization source, to the first ion detection region, and to the second ion detection region.

Abstract: The present invention is a device to restrict the sampling of analyte ions and neutral molecules from surfaces with mass spectrometry and thereby sample from a defined area or volume. In various embodiments of the present invention, a tube is used to sample ions formed with a defined spatial resolution from desorption ionization at or near atmospheric pressures. In an embodiment of the present invention, electrostatic fields are used to direct ions to either individual tubes or a plurality of tubes positioned in close proximity to the surface of the sample being analyzed. In an embodiment of the present invention, wide diameter sampling tubes can be used in combination with a vacuum inlet to draw ions and neutrals into the spectrometer for analysis. In an embodiment of the present invention, wide diameter sampling tubes in combination with electrostatic fields improve the efficiency of ion collection.

Abstract: The invention includes an ion mobility spectrometer having a liquid filled drift chamber. The chamber has an ionization region partitioned from and an ion separation region by a reversible ion-migration block. An electrical field within the chamber allows ions to migrate toward the electrode collector. Passage of ions from the ionization region is triggered by reversing the block allowing ions to migrate into the ion separation region. The invention includes a method of ion mobility analysis in liquid phase. Ions are mobilized to migrate through a drift liquid and are detected at an end of a drift chamber. The invention also includes a method of generating ions in a sample. A sample containing molecules in a first solvent is introduced into a second solvent through a charged capillary where the electrically charged sample is electro-disperses to ionize the molecules.

Abstract: One or more methods for determination and/or deconvolution of complex mass spectra, using quadrupole ion trap mass spectrometry.

Abstract: A novel instrument and method for TOF/TOF mass spectrometry is offered. A spiral trajectory time-of-flight mass spectrometer satisfies the spatial focusing conditions for the direction of flight and a direction orthogonal to the direction of flight whenever ions make a turn in the spiral trajectory. An ion gate for selecting precursor ions is placed in the spiral trajectory of the spiral trajectory time-of-flight mass spectrometer. Electric sectors are placed downstream of the ion gate.

Abstract: A method and apparatus for multiplexed data acquisition for gas-phase ion mobility coupled with mass spectrometry is described. Ion packets are injected into an ion mobility drift chamber at a rate faster than the ion mobility separation arrival time distribution. The convoluted arrival time distributions thus generated are deconvoluted by a mass spectrometer and post-processing algorithms.

Abstract: Aspects of the present invention are directed generally toward atom probe and three-dimensional atom probe microscopes. For example, certain aspects of the invention are directed-toward an atom probe or a three-dimensional atom probe that includes a sub-nanosecond laser to evaporate ions from a specimen under analysis and a reflectron for reflecting the ions. In further aspects of the invention, the reflectron can include a front electrode and a back electrode. At least one of the front and back electrodes can be capable of generating a curved electric field. Additionally, the front electrode and back electrodes can be configured to perform time focusing and resolve an image of a specimen.

Abstract: An ion detector includes collision surfaces for converting both positively and negatively charged ions into emitted secondary electrons. Secondary electrons may be detected using an electron detector, than may, for example include an electron multiplier. Conveniently, secondary electrons (or electrons emitted by the multiplier) may be detected using an electron pulse counter.

Abstract: A method for fragmentation of analyte ions for mass spectroscopy and a system for mass spectroscopy. The method produces gas-phase analyte ions, produces gas-phase radical species separately from the analyte ions, and mixes the gas-phase analyte ions and the radical species at substantially atmospheric pressure conditions to produce fragment ions prior to introduction into a mass spectrometer. The system includes a gas-phase analyte ion source, a gas-phase radical species source separate from the gas-phase analyte ion source, a mixing region where the gas-phase analyte ions and the radical species are mixed at substantially atmospheric pressure to produce fragment ions of the analyte ions, a mass spectrometer having an entrance where at least a portion of the fragment ions are introduced into a vacuum of the mass spectrometer, and a detector in the mass spectrometer which determines a mass to charge ratio analysis of the fragment ions.

Abstract: The present invention is a device to restrict the sampling of analyte ions and neutral molecules from surfaces with mass spectrometry and thereby sample from a defined area or volume. In various embodiments of the present invention, a tube is used to sample ions formed with a defined spatial resolution from desorption ionization at or near atmospheric pressures. In an embodiment of the present invention, electrostatic fields are used to direct ions to either individual tubes or a plurality of tubes positioned in close proximity to the surface of the sample being analyzed. In an embodiment of the present invention, wide diameter sampling tubes can be used in combination with a vacuum inlet to draw ions and neutrals into the spectrometer for analysis. In an embodiment of the present invention, wide diameter sampling tubes in combination with electrostatic fields improve the efficiency of ion collection.

Abstract: In a time-of-flight mass spectrometer with orthogonal ion injection performed by a pulser to which the ions are fed by an RF ion guide, compensation is provided for mass discrimination that occurs when the ions are injected into the pulser. This is accomplished by designing at least a part of the ion guide as an ion storage device, by emptying the filled ion storage device mass-selectively in ion groups, group-by-group, and by serially feeding the ion groups to the pulser with correct timing, using the mass selectivity of the pulser filling process to compensate for the mass discrimination.

Abstract: A mass spectrometer is disclosed comprising a first quadrupole rod set mass filter (7), a collision cell (8), an ion mobility spectrometer or separator, an ion guide or collision cell (13) arranged downstream of the ion mobility spectrometer or separator, a second quadrupole rod set mass filter (16) and an ion detector (15).

Abstract: An apparatus and method for measuring low or trace concentrations of compounds and mixture of gases. A method and apparatus of the invention permits separating ions of different mobilities by passing them through an abrupt change or step in electric field magnitude. By using the separation method, the compounds of interest may be measured with less interference from other compounds of the gas mixture, which reduces or eliminates the need for prior separation of the components of the gas mixture. Several embodiments of the invention are described including the use of current amplifiers on one, or more, parts of the apparatus. While a single screen can provide a chamber which is divided into two regions of different electric fields, it is within the scope of the invention to include multiple screens to provide several steps in the electric field permitting it to be possible to trap and measure ions with successively higher mobilities.

Abstract: A detector apparatus supplies samples of gas or vapour to an ion mobility spectrometer (1) via a tube (2). The tube is made of fluorinated ethylene propylene selected to reduce adhesion of substances of interest to the tube, which may also be heated along its length further to reduce adhesion. The tube (2) is closely spaced from the inlet orifice (10) of the spectrometer 1 and opens into an enclosure (3) housing a fan (4), which draws gas and vapour through the tube. The tube (2) may be flexible and extend for some distance to enable sampling from locations remote from the spectrometer (1).

Abstract: The present invention is a device to restrict the sampling of analyte ions and neutral molecules from surfaces with mass spectrometry and thereby sample from a defined area or volume. In various embodiments of the present invention, a tube is used to sample ions formed with a defined spatial resolution from desorption ionization at or near atmospheric pressures. In an embodiment of the present invention, electrostatic fields are used to direct ions to either individual tubes or a plurality of tubes positioned in close proximity to the surface of the sample being analyzed. In an embodiment of the present invention, wide diameter sampling tubes can be used in combination with a vacuum inlet to draw ions and neutrals into the spectrometer for analysis. In an embodiment of the present invention, wide diameter sampling tubes in combination with electrostatic fields improve the efficiency of ion collection.

Abstract: An electrospray-assisted laser desorption ionization device includes: an electrospray unit including a nozzle; a voltage supplying member disposed to establish between the nozzle and a receiving unit a potential difference such that liquid drops of the electrospray medium formed at the nozzle are laden with charges, and such that the liquid drops are forced to leave the nozzle toward the receiving unit along a traveling path; a laser desorption unit adapted to irradiate a sample such that, upon irradiation, analytes contained in the sample are desorbed to fly along a flying path which intersects the traveling path so as to enable the analytes to be occluded in the liquid drops, and such that as a result of dwindling in size of the liquid drops when moving along the traveling path, charges of the liquid drops will pass on to the analytes occluded therein to form ionized analytes.

Abstract: The invention provides a security inspection system for inspecting persons, characterized in that it comprises: a passageway which provides an inspection space isolated or partially isolated from an ambient environment, in which at least one sub-passageway allowing persons to be inspected to pass is provided in the inspection space, and each of the sub-passageways is provided with at least one millimeter wave imaging device for millimeter wave imaging of persons being inspected; and an ion mobility spectrometer for ionizing particles of substance or gases that are released or volatilized from the inspected persons into the air in the passageway and then measuring a mobility rate thereof under the action of the electric field to effect identification of substances. At least one radioactive substance inspection device may also be provided in the passageway to detect whether the person being inspected carries radioactive substances.

Abstract: The present invention provides a mass spectrometer including an ion source for generating pre-cursor ions, ion fragmentation means for generating fragment ions from the pre-cursor ions, a reflectron for focusing the kinetic energy distribution of the ions, and an ion detector wherein the mass spectrometer also includes axial spatial distribution focusing means which in use acts on the ions after the ion fragmentation means and before the reflectron, the axial spatial distribution focusing means being operable to reduce the spatial distribution of the ions in the direction of the ion optical axis of the spectrometer. Suitably the axial spatial distribution focusing means comprising a cell with two electrodes 52, 54 which may be apertures or high transmission grids. A pulsed electrostatic field is generated by applying a high voltage pulse 60 to the first electrode 52 at the time when the pre-cursor ions of interest 56, 58 have just passed into the pulser 50.

Abstract: Auxiliary electrodes for creating drag fields may be provided as arrays of finger electrodes on thin substrates such as printed circuit board material for insertion between main RF electrodes of a multipole. A progressive range of voltages can be applied along lengths of the auxiliary electrodes by implementing a voltage divider that utilizes static resisters interconnecting individual finger electrodes of the arrays. Dynamic voltage variations may be applied to individual finger electrodes or to groups of the finger electrodes.

Abstract: Apparatus and method for generating ammonia gas. In one aspect, a method for generating ammonia gas for use in an ion mobility spectrometry (IMS) system is provided. The method includes inserting a device into a space defined within the IMS system, the device including an ammonia compound. The method also includes activating to decompose and to produce the ammonia gas without producing water vapor. The method also includes emitting the ammonia gas into the IMS system.

Abstract: The TOF mass spectrometer disclosed places an even number of ion mirrors in close proximity to a MALDI ion source and a field-free drift space between the exit from the mirrors and an ion detector. This “reversed geometry” configuration may be distinguished from a conventional reflecting TOF analyzer employing a single ion mirror where a large fraction of the total drift space is located between the ion source and the mirror.

Abstract: A Time of Flight mass analyser is disclosed comprising an ion detector comprising an Analogue to Digital Converter. Output signals from the ion detector are digitised and the arrival times and intensity values relating to ion arrival events are determined. If the determined arrival times from two signals fall within the same time window then the arrival times are added together in a weighted manner and the intensity values are combined.

Abstract: The invention relates to a test method, especially for mass spectroscopy of biomolecules, including the following steps: one or several samples (2-4) that are to be analyzed are introduced into a carrier liquid of a micro liquid jet (1) in rapid succession; at least some of the samples (2-4) are desorbed from the micro liquid jet (1); and the sample (2-4) that is desorbed from the micro liquid jet (1) is analyzed. According to the invention, the sample (2-4) is spatially delimited in the spraying direction in the micro liquid jet (1) while extending only along a subarea of the micro liquid jet (1) in the spraying direction.

Abstract: A method includes: accumulating ions having a plurality of m/z values in an ion trap during a time interval; deriving from the accumulated ions a respective intensity value for each of the m/z values; and adjusting each of the intensity values as a function of the time needed by the ion trap to begin collecting ions with the corresponding m/z value. According to a different aspect, an apparatus includes a first portion with an ion trap, and a second portion. The second portion causes the ion trap to accumulate ions with a plurality of m/z values during a time interval, derives from the accumulated ions in the ion trap a respective intensity value for each of the m/z values, and adjusts each of the intensity values as a function of the time needed by the ion trap to begin collecting ions with the corresponding m/z value.

Abstract: An interface that couples SPME to IMS has been constructed and evaluated for the detection of the following detection taggants: 2-nitrotoluene (2-NT), 4-nitrotoluene (4-NT), and 2,3-dimethyl-2,3-dinitrobutane (DMNB). The interface was also evaluated for the following common explosives: smokeless powder (nitrocellulose, NC), 2,4-dinitrotoluene (2,4-DNT), 2,6-dinitrotoluene (2,6-DNT), 2,4,6-trinitrotoluene (2,4,6-TNT), hexahydro-1,3,5-trinitro-s-triazine (RDX), and pentaerythritol tetranitrate (PETN). The resultant SPME-IMS interface was found to extract volatile constituent chemicals and detection taggants in explosives from a headspace for subsequent detection in a simple, rapid, sensitive, and inexpensive manner.

Abstract: Enantiomers are characterized, identified, synthesized and/or modified with a shaped laser pulse. In another aspect of the present invention, binary shaping and circular polarization are employed with a laser pulse. A further aspect of the present invention provides a quarter-wave plate in combination with one or more pulse shapers.

Abstract: A mass spectrometer is disclosed comprising an ion mobility spectrometer or separator (3) arranged upstream of a collision or fragmentation cell (5). Ions are separated according to their ion mobility within the ion mobility spectrometer or separator (3). The kinetic energy of the ions exiting the ion mobility spectrometer or separator (3) is increased substantially linearly with time in order to optimize the fragmentation energy of ions as they enter the collision or fragmentation cell (5).

Abstract: A method for operating a mass spectrometer includes determining a first performance characteristic while operating the mass spectrometer with a first electron emitter, storing first information relating to the first performance characteristic, determining a second performance characteristic while operating the mass spectrometer with a second electron emitter, storing second information relating to the second performance characteristic, and thereafter switching from operation using the first electron emitter to operation using the second electron emitter. The switching includes using the first and second information to normalize performance of the second electron emitter after the switching relative to performance of the first electron emitter before the switching.

Abstract: The invention provides an ion extraction pulser. The ion extraction pulser may be used independently or in conjunction with a mass spectrometry system. The mass spectrometry system includes an ion source for producing ions, an ion optics system downstream from the ion source for selecting and directing ions, and a detector down stream from the ion optics system for detecting the ions selected and directed by the ion optics system. The ion optics system includes one or more ion extraction pulsers.

Abstract: Method and apparatus for high field asymmetric waveform ion mobility spectrometry in an electronic chip assembly, including an input section, an ion filter and detection section and a control section, in which ion filtering proceeds in a planar chamber under influence of high field asymmetric periodic signals, with detection integrated into the flow path, for producing accurate, real-time, data for identification of a broad range of chemical compounds.

Abstract: A system and method for providing a pulsed atmospheric source of ions for chemical analysis includes a chamber containing a pair of electrodes and a second chamber with the sample gas. A narrow pulse of high voltage is applied between the electrodes to form an arc which emits ultraviolet light directly into the sample gas chamber through an aperture connecting the chambers. The ultraviolet photons ionize the sample gas and the resultant sample gas ions are then swept into a chemical detector by an electric field.

Abstract: The present invention relates to a method and apparatus for ion fragmentation by electron capture. The present invention provides a method of generating fragment ions by electron capture, comprising; directing ions to be fragmented into a fragmentation chamber of a mass spectrometer into a fragmentation chamber of a mass spectrometer arrangement; trapping at least some of the ions to be fragmented in at least one direction of the fragmentation chamber by using a magnetic field, the ions being trapped within a volume V; generating an electron beam using an electron source located away from the volume V; irradiating the trapped ions in the volume V with the electrons generated by the electron source in the presence of the said magnetic field, so as to cause dissociation; and ejecting the resultant fragment ions from the fragmentation chamber for subsequent analysis at a different location away from the fragmentation chamber.

Abstract: A linear ion trap traps a plurality of charged particles in a charged particle trap including first and second electrode mirrors arranged along an axis at opposite ends of the particle trap, the electrode mirrors being capable, when voltage is applied thereto, of creating respective electric fields configured to reflect charged particles causing oscillation of the particles between the mirrors. The method includes: (a) introducing into the charged particle trap the plurality of charged particles, the particles having a spread in the oscillation time of the particles per oscillation; (b) applying voltage to the electrode mirrors during step (a) to induce a relatively weak self-bunching of the charged particles; and (c) after the plurality of charged particles has been introduced into the charged particle trap, waiting for a time period ?T and then changing the voltage so as to induce a relatively stronger self-bunching among the charged particles.

Abstract: A compact integrated ion mobility based analysis system includes at least one gas chromatograph (GC) column that receives a sample and elutes constituents of the sample where each of the eluted constituents are temporally separated from each other The system also includes at least one ion mobility based sample analyzer that analyzes the eluted constituents based on their ion mobility characteristics. The system further includes a controller that selectively adjusts the temperature within at least one GC column over a period of time and selectively adjusts the temperature within at least one ion mobility based sample analyzer over a period of time.

Abstract: In a system for analyzing samples by mass spectrometry, analyte ions are analyzed first by field asymmetric ion mobility spectrometry (FAIMS) before being analyzed by a mass analyzer. The analyte ions are produced in an ion source operating at near atmospheric pressure and transferred via a dielectric capillary into the vacuum system of the mass analyzer. While passing through the capillary, the ions are analyzed by FAIMS via electrodes on the interior wall of the capillary.

Abstract: A tandem mass spectrometer operable to determine properties of chemical and biochemical compounds (analytes) comprises an ion source, a monopole ion processing cell positioned to receive primary ions from the ion source and a mass analyzer positioned to receive secondary ions output from the monopole ion processing cell. The monopole ion processing cell comprises an elongate inner electrode and an elongate outer electrode radially offset from and partially surrounding the inner electrode. In one embodiment, the elongate inner and outer electrodes of monopole ion processing cell are segmented, and at least one of the outer electrode segments defines an axial slot through which the secondary ions are radially output to the mass analyzer.

Abstract: In a multipole rod ion guide system operated with RF voltages to collect or transmit ions, the inhomogeneity of the electric RF fields is increased in front of the ion guide rods by forming the rod surfaces from a plurality of spaced electrodes. The inhomogeneous fields produced by the plurality of electrodes increases the mass range over which the ions are guided effectively while still maintaining a pseudopotential minimum which is as well defined as possible close to the axis. Particularly favorable ion guides of this type make it possible to apply an axial DC field to the guide system for the active transport of the ions.

Abstract: Many applications in the study of metabolics and proteomics require measurements on peptides and small molecules with high resolving power and mass accuracy. These are often present in complex mixtures and sensitivity over a relatively broad mass range, speed of analysis, reliability, and ease of use are very important. The present invention is a time-of-flight mass spectrometer providing optimum performance for these and similar applications.

Abstract: The invention relates to a gas analysis based on the mobility of ions. The invention relates to a cell structure of an analysis device, the cell structure comprising the reference cell (201), the ionisation section (202) and the analysis cell (203) for identifying the electric mobility of ions. The invention also relates to a method for identifying the ions. Further, the invention relates to a system for identifying the ions.

Abstract: A system for the stand-off detection of trace amounts of analyte materials such as explosives, chemical warfare agents, toxic industrial chemicals, and the like includes an ion source that is operably connected to an ion collection means and to a sensor. The ion source employs a first gas that is passed through an electrical discharge to produce metastable gas molecules as well as charged particles of various kinds. Ions and other charged particles are removed from the first gas which is then reacted with a second gas having a lower ionization potential to obtain reactant ions of relatively uniform energy. The reactant ions are focused and accelerated into a beam that is directed upon a surface, such as luggage or clothing that is being interrogated, to produce analyte ions which are collected and passed into the sensor that is preferably a differential mobility spectrometer.

Abstract: A method for mass-spectrometric detection of compounds in a gas flow includes: alternatingly forming first and a second beams by switching between electron pulses/pulse trains and photon pulses/pulse trains, the photon pulses/pulse trains being generated by an excimer lamp, and the switching between the electron pulses/pulse trains and the photon pulses/pulse trains occurring at a switching frequency above 50 Hz; disposing the gas flow in an ionization region crossed by the first and second beams so as to ionize volume units in the gas flow so as to form ions of the compounds; deflecting the ions in an effective region of an electric field to a mass-spectrometric device; and sensing the ions with a mass-spectrometric process of the mass-spectrometric device.

Abstract: The present invention provides an ion selector gate having a first deflection zone 32 and a second deflection zone 34 spaced from the first deflection zone, wherein in use, a single low voltage trigger pulse generated by timing electronics with a width in time equal to or proportional to the width of the gate pulse Tgd and at a position in time that the ion gate is required to be open to allow through ions of the correct nominal mass. The trigger pulse may go through an inverter 38 and then to two high voltage pulsers 40 and 42. The high voltage pulsers each produce simultaneously a signal that switches to ground and back on again from the same amplitude high voltage but the opposite polarity. The outputs of the high voltage pulsers are connected to interleaved wires of both ion gates 32, 34. Thus, the high voltage pulsers are applied simultaneously to both ion gates.

Abstract: Disclosed herein are systems, methods and apparatus, for detection and identification of chemical warfare agents (CWAs) using a differential mobility spectrometer.

Abstract: Various embodiments of a multi-dimensional ion mobility analyzer are disclosed that have more than one drift chamber and can acquire multi-dimensional ion mobility profiles of substances. The drift chambers of this device can, for example, be operated under independent operational conditions to separate charged particles based on their distinguishable chemical/physical properties. The first dimension drift chamber of this device can be used either as a storage device, a reaction chamber, and/or a drift chamber according to the operational mode of the analyzer. Also presented are various methods of operating an ion mobility spectrometer including, but not limited to, a continuous first dimension ionization methods that can enable ionization of all chemical components in the sample regardless their charge affinity.

Abstract: An explosive detection system based on an ion mobility spectrometer detects the presence of trace molecules in air. Such instruments require an ion source to ionize the trace molecules. An ion source that does not require a radioactive source to operate can use the photoelectric effect to produce electrons. Such a photoelectric ion source will gradually be contaminated and lose its photoelectron emission properties when operated in the air. The photocathode of the ion source can be automatically regenerated by a heater in thermal communication with the photocathode. The heater may be activated when the photoelectron emission falls below a predetermined value ro may run or cycle continuously.

Abstract: A system for the non-contact detection of analyte chemicals, including explosives, chemical warfare agents and the like, employs a non-equilibrium plasma that is maintained at a temperature sufficiently low so as to avoid thermal damage to a surface, such as clothing or skin, that is being examined to thereby produce analyte ions and other charged particles. The ions are collected and passed into a sensor for detection and identification.

Abstract: A mass spectrometer and a technique for operating it involve setting an operating parameter that influences a rate of flow of electrons from an electron source into an ion volume so that ions produced from a material in the ion volume in response to electrons satisfy an ion production target, performing a plurality of analytical runs using the mass spectrometer with the electron source while monitoring an operational characteristic, and adjusting the operating parameter in response to the monitoring to compensate for a change over time in the operational characteristic in a manner so that the ion production target remains satisfied.

Abstract: The present invention relates generally to grids for gating a stream of charged particles and methods for manufacturing the same. In one embodiment, the present invention relates to a Bradbury-Nielson gate having transmission line grid elements. In one embodiment is a feed structure for a gating grid where a drive source is coupled to a feeding transmission line with the same geometry as the chopper and continues with the same geometry to a termination transmission line. Also included is a method for fabricating a gate for charged particles which includes micromachining at least two gate elements from at least one wafer, wherein each gate element includes at least one grid element; metalizing the grid elements; and assembling the gate elements such that the grid elements of the gate elements are interleaved, thereby forming a Bradbury Nielson gate.

Abstract: The present invention provides a device, system, and associated methods to actively or passively sample air by directing it onto the surface of a porous light-absorbing semiconductor, for example, a desorption/ionization on porous silicon (“DIOS”) chip. Upon adsorption of an analyte, the surface may be analyzed directly by laser desorption/ionization time-of-flight mass spectrometry. Because the process of laser desorption/ionization and subsequent mass detection does not require elevated temperatures, thermal degradation of analytes is avoided.

Abstract: Particular aspects provide novel methods for analysis of ion populations, the methods comprising filtering and selecting an ion population using a low-field dual-gate ion mobility spectrometer comprising a drift tube, the spectrometer operating at a pressure of at least 100 Torr, to provide mobility-selected ions. Certain aspects comprise: (i) subsequently accumulating the low-field selected ions in an ion trap (e.g., an MS ion trap) and mass spectrometry analysis; (ii) introducing the low-field selected ions into a high-field ion mobility spectrometer for separating thereby (optionally followed by mass spectrometry); and (iii) introducing the low-field selected ions into an ion trap mass spectrometer, and subsequently into a second low-field ion mobility spectrometer (e.g., a non-dual gate spectrometer operating at less than about 100 Torr). Additional aspects provide novel apparatus and combination thereof for performing the disclosed methods.