A method of ion mobility and/or mass spectrometry is disclosed in which the ion mobility and/or mass to charge ratio of an ion is determined using an algorithm or relationship that relates the transit time or average ion velocity of the ion through an ion separation device in which one or more time-varying electric field is used to separate ions passing therethrough to one or more parameters for the device, the mass to charge ratio of the ion and the ion mobility of the ion.

A mass spectrometer collision cell system, comprising: a gas containment vessel comprising an internal chamber having ion inlet and ion outlet ends and a cross-sectional area, A.sub.chamber; a gas inlet aperture; first and second gas outlet apertures that are disposed at or proximal to the ion inlet and outlet ends, respectively, and that have respective outlet aperture cross-sectional areas, A.sub.aperture1 and A.sub.aperture2, and an average outlet aperture cross-sectional area, A.sub.aperture.sup.ave; a longitudinal axis of the chamber extending from the ion inlet end to the ion outlet end and having a length, L.sub.chamber; and a set of multipole rod electrodes, at least a portion of each multipole rod electrode being within the chamber, wherein the values of A.sub.chamber, L.sub.chamber and A.sub.aperture.sup.ave are such that the combined gas conductance of the chamber and the gas outlet apertures is not greater than 95 percent of the gas conductance of the gas outlet apertures alone.

Apparatus comprise an electrode arrangement comprising a plurality of electrodes defining a volume, an ion entrance, and an ion exit, and a voltage source coupled to the plurality of electrodes and configured to apply a nonlinear DC voltage sequence to the electrodes between the ion entrance and the ion exit that directs ions through the volume with the volume at a pressure of at least 1 Torr. Ions can be focused using nonlinear DC voltage sequences, including at atmospheric pressure. Related methods are also disclosed.

A mass spectrometry method comprises: receiving a stream of ions at an inlet end of an ion transport device; accumulating a first portion of the ion stream at a first electrical potential well at a first position within the ion transport device between the inlet and outlet ends; creating a generally descending potential profile within the ion transport apparatus between a second position and the outlet end and, simultaneously, creating a second potential well at a third position within the ion transport apparatus, the second position disposed between the first position and the inlet end, the third position disposed between the second position and the inlet end; and transporting the accumulated first portion of the ion stream from the first position to the outlet end under the impetus of the generally descending potential profile and, simultaneously, accumulating a second portion of the ion stream at the second potential well.

An instrument for separating ions may include an ion source configured to generate ions from a sample, at least one ion separation instrument configured to separate the generated ions as a function of at least one molecular characteristic and an electrostatic linear ion trap (ELIT) positioned to receive ions exiting the at least one ion separation instrument. The ELIT has first and second ion mirrors separated by a charge detection cylinder, and is configured such that an ion trapped therein oscillates back and forth through the charge detection cylinder between the first and second ion mirrors with a duty cycle, corresponding to a ratio of time spent by the trapped ion traversing the charge detection cylinder and total time spent by the trapped ion traversing a combination of the first and second ion mirrors and the charge detection cylinder during one complete oscillation cycle, of approximately 50%.

A method and apparatus for separating ions according to a physicochemical property, such as ion mobility or mass-to-charge-ratio, is disclosed, comprising: repeatedly travelling a transient DC voltage along an ion guide; wherein the transient DC voltage has a first amplitude and first speed whilst it travels along a first region of the ion guide so as to urge ions having different values of said physicochemical property through said first region of the ion guide with different average speeds; and wherein, in a first mode, the transient DC voltage is travelled along a second region of the ion guide that is adjacent to said first region: (i) whilst having a second different amplitude; and/or (ii) at a second different non-zero speed; and/or (iii) at a substantially constant speed but with a different frequency to which it is repeatedly travelled along the first region; so that ions having a given value of said physicochemical property are urged through said second region of the ion guide at a different average speed than they are urged through the first region, thereby causing the ions to be spatially compressed or expanded as they pass from the first region of the ion guide to the second region.

An ion mobility separator comprises an RF-device for transversely confining ions in an ion region using: (a) a first set of electrodes arranged parallel to one another along a direction of ion travel to define a first transverse boundary of the ion region, and that are supplied with a first RF-voltage such that different phases of the first RF-voltage are applied to adjacent electrodes of the first set; and (b) a second set of electrodes arranged parallel to one another along said direction of ion travel to define a second transverse boundary of the ion region, and that are supplied with a second RF-voltage such that different phases of the second RF-voltage are applied to adjacent electrodes of the second set, the first and second transverse boundaries being substantially opposite each other in a transverse direction of the ion region and the first and second RF voltages having different frequencies.

A method is disclosed comprising: trapping ions in an ion trap (40); applying a first force on the ions within the ion trap in a first direction, said force having a magnitude that is dependent upon the value of a physicochemical property of the ions; applying a second force on these ions in the opposite direction so that the ions separate according to the physicochemical property value as a result of the first and second forces; and then pulsing or driving ions out of one or more regions of the ion trap.

A circuit and method for providing high-voltage radio-frequency (RF) energy to an instrument at multiple frequencies includes a plurality of inputs each configured to receive an RF voltage signal oscillating at a corresponding frequency, and a step-up circuit for generating magnified RF voltage signals based on the received RF voltage signals. The step-up circuit includes an LC network operable to isolate the RF voltage signals at the plurality inputs from one another while preserving a voltage magnification from each input to a common output at each of the corresponding frequencies.

An ion guide or mass analyser is disclosed comprising a plurality of electrodes having apertures through which ions are transmitted in use. A pseudo-potential barrier is created at the exit of the ion guide or mass analyser. The amplitude or depth of the pseudo-potential barrier is inversely proportional to the mass to charge ratio of an ion. One or more transient DC voltages are applied to the electrodes of the ion guide or mass analyser in order to urge ions along the length of the ion guides or mass analyser. The amplitude of the transient DC voltage applied to the electrode may be increased with time so that ions are caused to be emitted from the ion guide or mass analyser in reverse order of their mass to charge ratio.