Patent ID: 8173959

Claim:
A system for analyzing materials at or near atmospheric pressure, comprising: a sampling inlet that receives a input sample to be analyzed; an ion source to ionize the input sample to produce an ionized sample; a drift tube ion mobility spectrometer (IMS) stage having an IMS inlet that receives the ionized sample and having an IMS outlet, the IMS stage having a time-independent electrical field that is applied to the ionized sample to move the ionized sample toward the IMS outlet, the IMS stage identifying the ionized sample based on time of arrival at the IMS outlet; a high-field asymmetric-waveform ion mobility spectrometer (FAIMS) operating as a differential mobility spectrometer (DMS) stage coupled in series with the IMS stage to receive the ionized sample from the IMS stage; a fast Faraday detector to analyze the ionized sample exiting the DMS stage; and a sample vacuum pump to cause the ionized sample to flow through the system, wherein the IMS stage comprises an ion mobility drift cell having a first ion gate and a second ion gate, the system further comprising a system controller that controls the release, the acceleration, and the timing of packets of ions produced in the ion source by controlling the first ion gate and the second ion gate of the ion mobility drift cell, the system controller selectively operating the first ion gate and the second ion gate in a first mode of operation and a second mode of operation, wherein: in the first mode of operation: the system controller opens the first ion gate for a selected duration at the beginning of each detection cycle to inject a packet of ions into the IMS for pre-separation; the system controller opens the second ion gate throughout the detection cycle; and the IMS stage producing an IMS spectrum by measuring the ion current in a Faraday detector in the IMS stage while the second ion gate remains open; and in the second mode of operation: the system controller opens the first ion gate for a selected duration at the beginning of each detection cycle to inject a packet of ions into the IMS stage; and the system controller pulses the second ion gate open at a selected time after opening the first ion gate to control the ion flow by allowing only ions in selected peaks or in a section of the mobility spectrum to be transferred to the DMS stage in accordance with the travel time of the preselected analyte to be detected by the Faraday detector.