A dual-polarity ion mobility spectrometer for capturing hyper-fast chromatographic peaks

Abstract

For higher analytical performance, ion mobility spectrometers (IMS), especially when analyzing complex mixtures, are often coupled with gas chromatographs (GC). However, analysis time remains a critical parameter in gas chromatography. Therefore, a hyper-fast GC is a promising approach for GC-IMS to combine highest sensitivity of IMS with increased peak capacity while allowing for rapid analysis within the double-digit second range. For simultaneously recording of both ion polarities, a new dual drift tube IMS in axial configuration has been developed that is particularly designed for resolving even hyper-fast GC peaks. Key is a directed sample gas flow through the ionization region giving a small effective detector volume. To avoid condensation of the sample gas, the IMS is isothermally heated to 120 °C. A drift tube length of only L_D = 41 mm with a drift voltage of U_D = 2.7 kV leads to an IMS repetition rate of 100 Hz and high resolving power of R_p = 60, even for ions with low reduced ion mobility down to 0.43 cm²V^-1s^-1. This setup can resolve very short GC peaks with full width at half maximum of only 140 ms. For demonstration, two different hop varieties and a mixture of explosives were analyzed within a short time of just 20 s.