Micro Faraday-Element Array Detector for Ion Mobility Spectroscopy

The novel ion mobility spectrometry (IMS) includes a drift tube having a collecting surface covering a collecting area at one end of the tube. The surface comprises a plurality of closely spaced conductive elements on a non-conductive substrate, each conductive element being electrically insulated from each other element. A plurality of capacitive transimpedance amplifiers (CTIA) adjacent the collecting surface are electrically connected to the plurality of elements, so charge from an ion striking an element is transferred to the capacitor of the connected CTIA. A controller counts the charge on the capacitors over a period of time.
 

Background:

Ion mobility spectrometry (IMS) is an analytical technique used to separate and identify ionized molecules in the gas phase based on their ion mobility in a carrier buffer gas. Detection limit using a Faraday cup is around six thousand ions per second in the most expensive isotope ratio mass spectrometers. This corresponds to one femtoamp of current. It takes very sophisticated electronics to measure this small current with any certainty. The direct current measuring devices used in prior art ion mobility spectrometers are able to only measure currents in the picoamp range.
 

Advantages:

• This new IMS detector technique raises the detection limit of the device three orders of magnitude to over six million ions per second
• Advance selectivity through the addition of a reliable and fast GC inlet
• Enhance instrument performance through advances in sampling
• Improve detection limits by limiting fragmentation of ions

Applications:

• Some of these improvements are specific for explosives
• Increase speed or economy through small, mass produced analyzers
• Heavily employed for military or security purposes, such as detecting drugs and explosives
• Many laboratory analytical applications, recently being coupled with mass spectrometry and high performance liquid chromatography