Parallel plate geometry FAIMS apparatus and method

An apparatus for separating ions, comprising a high field asymmetric waveform ion mobility spectrometer, including:

• a) an analyzer region comprising:
• a first electrode, a second electrode and a third electrode in a spaced apart stacked arrangement for allowing ion flow therebetween, the first electrode having a first inner surface, the second electrode having a continuous smoothly curved surface, the third electrode having a second inner surface;
• and,
• at least a contact on at least one of the first, second and third electrodes, for receiving a compensation voltage potential between the second and first electrodes and between the second and third electrodes, and for applying an asymmetric waveform to at least one of the electrodes.

An apparatus for separating ions, comprising a high field asymmetric waveform ion mobility spectrometer, including:

• a first electrode having first and second facing surface regions;
• a second electrode disposed between the first and second facing surface regions, the second electrode including a first surface spaced apart from and approximately parallel to the first surface region of the first electrode to define a first analyzer region for separating ions, and a second surface spaced apart from and approximately parallel to the second surface region of the first electrode to define a second analyzer region for separating ions;
• and,
• at least a contact on at least one of the first and second electrodes, for applying a compensation voltage potential between the second and first electrodes, and for receiving an asymmetric waveform to at least one of the first and second electrodes,
• wherein the second electrode prevents fluid communication between the first and second analyzer regions while the ions are being separated, and wherein, in use, ions exiting from between the electrodes are other than attracted to the second electrode, such that the ions other than collide therewith.

An analyzer comprising:

• an outer electrode having a curved inner surface defining an internal cavity, an inlet through a first portion of the curved inner surface for introduction of ions and a carrier gas into an inlet region proximate the inlet, and an outlet through a second portion of the curved inner surface for extracting ions from an outlet region proximate the outlet;
• an inner electrode disposed within the internal cavity of the outer electrode and having a curved outer surface maintaining an approximately uniform space to the curved inner surface of the outer electrode, the approximately uniform space defining a curved analyzer region extending between the inner and outer electrodes for separating ions propagating therethrough;
• and,
• at least a contact on at least one of the inner and outer electrodes for receiving a compensation voltage potential between the inner and outer electrodes, and for applying an asymmetric waveform to at least one of the inner and outer electrodes,
• wherein, ions that have appropriate high field mobility properties for the combination of applied compensation voltage and asymmetric waveform are selectively transmitted through the curved analyzer region between the inlet region and the outlet region along a continuously curving ion flow path absent a portion having a substantially linear component, and wherein a similar electric field is present at the inlet region and at the outlet region.

A method for separating ions comprising the steps of:

• a) providing at least an ionization source for producing ions including two ionic species;
• b) providing an analyzer including a first analyzer region defined by a space between a first electrode surface on a first electrode plate and an opposing second electrode surface on a second electrode plate;
• c) providing an asymmetric waveform and a direct-current compensation voltage, to at least one of said electrode surfaces, to form an electric field between the first electrode surface and the opposing second electrode surface;
• d) setting said asymmetric waveform in order to effect a difference in net displacement between said two ionic species in the time of one cycle of said applied asymmetric waveform;
• e) setting said compensation voltage to a determined value to support selective transmission of one of said two ionic species within the first analyzer region;
• f) providing ions from the ionisation source into the first analyzer region;
• g) conducting the ions through the first analyzer region toward an outlet of the analyzer;
• and,
• h) providing an electric field on a side of the first electrode plate that is opposite the first surface, such that a substantial portion of the ions exiting from the first analyzer region avoid a collision with the first electrode plate.

A method for separating ions comprising the steps of:

• providing an ionization source for producing ions including two ionic species;
• providing an analyzer region defined by an approximately uniform space between inner and outer electrodes and extending between an inlet region and an outlet region;
• introducing a flow of ions including two ionic species into the inlet region;
• transporting said ions through the analyzer region along a continuously curving ion flow path extending from the inlet region to the outlet region;
• forming an electric field within the analyzer region by providing an asymmetric waveform and a direct-current compensation voltage to at least one of the inner electrode and the outer electrode;
• setting said asymmetric waveform and said compensation voltage to a determined value to selectively focus one of said two ionic species;
• and,
• extracting said selectively focused one of said two ionic species at the outlet region.

A method for separating ions comprising:

• a) providing at least an ionization source for producing ions including two ionic species;
• b) providing an analyzer including a first analyzer region defined by a space between a first electrode surface on a first electrode plate and an opposing second electrode surface on a second electrode plate;
• c) providing an asymmetric waveform and a direct-current compensation voltage, to at least one of said electrode surfaces, to form an electric field between the first electrode surface and the opposing second electrode surface;
• d) setting said asymmetric waveform in order to effect a difference in net displacement between said two ionic species in the time of one cycle of said applied asymmetric waveform;
• e) setting said compensation voltage to a determined value to support selective transmission of one of said two ionic species within the first analyzer region;
• f) providing ions from the ionisation source into the first analyzer region;
• g) conducting the ions through the first analyzer region toward an outlet of the analyzer;
• and,
• h) providing an electric field on a side of the first electrode plate that is opposite the first electrode surface, such that a substantial portion of the ions exiting from the first analyzer region avoid a collision with the first electrode plate,
• wherein providing an electric field on a side of the first electrode plate that is opposite the first electrode surface comprises providing a second different analyzer region defined by a space between a third electrode surface on the first electrode plate and an opposing fourth electrode surface that is other than on the first electrode plate, the first electrode surface and the third electrode surface disposed on opposite sides of the first electrode.