Phase-resolved detection in ion-mobility spectrometry

Throughput has been improved in an ion-mobility spectrometer by means of continuous ion-beam modulation and phase-resolved detection. Conventional ion-mobility spectrometry (IMS) utilizes brief packets of ions for separation in the gas phase. In contrast, this preliminary report outlines a new detection method based on phase resolution and involves monitoring the ion signal continuously, which raises the duty cycle of the instrument froth approximately 1% (conventional IMS) to 50%. The greater duty cycle is shown to improve signal-to-noise ratios (SIN). However, the higher SIN levels did not translate into higher sensitivity values when calibration plots were constructed. It is demonstrated that even analytes with small differences in drift times can be modulated at frequencies that maximize the measured phase differences between ions. Phase-resolved signals can be processed with a Fourier transform and chemometric data reduction to simplify identification of the analyte from its phase spectra. (c) 2006 Elsevier B.V. All rights reserved.