Hadamard Transform Ion Mobility Spectrometry

Abstract

A detection scheme that makes use of the Hadamard transform has been employed with an atmospheric-pressure ion mobility spectrometer fitted with an electrospray ionization source. The Hadamard transform was implemented through the use of a linear-feedback shift register to produce a pseudorandom sequence of 1023 points. This pseudorandom sequence was applied to the ion gate of the spectrometer, and deconvolution of the ion signal was accomplished by the Hadamard transform to reconstruct the mobility spectrum. Ion mobility spectra were collected in both a conventional and Hadamard mode, with comparisons made between the two approaches. Initial results exhibited low spectral definition, so an oversampling technique was applied to increase the number of data points across each analyte spectral peak. The use of the Hadamard transform increases the duty cycle of the instrument to 50% and results in a roughly 5-fold enhancement of the signal-to-noise ratio with a negligible loss of instrument resolution. It is also shown that any potential multiplex disadvantage, which limits the attractiveness of some high-throughput techniques, is not a limiting factor in this new implementation.

Biomolecule Analysis by Ion Mobility Spectrometry

“…Thus, for a continuous ion source, the introduction of a short pulse of ions upon initiation of experiments often limits duty cycles. Researchers have used a number of approaches (including utilizing multiple injections, as well as Fourier and Hadamard transform approaches) to improve duty cycles (100)(101)(102). Alternatively, at low pressures, it is possible to store ions for extended times to accumulate continuous signals into concentrated packets.…”

Multidimensional Separation of Natural Products Using Liquid Chromatography Coupled to Hadamard Transform Ion Mobility Mass Spectrometry

“…Previous reports showed no significant change of resolving power in Hadamard mode compared with pulsed mode [46,47]; here we compare the 15 major mobility peaks. Though we used 20% wider gating pulse in HT mode, the raw resolving power was not less than in pulsed mode.…”

Progress on Ion Beam Modulation Technique for Time-Dependent Analytical Instruments

“…Ion beam modulation based on Hadamard transform have presented by Hadamard transform time-of-flight mass spectrometry (HT-TOFMS) [16] and Hadamard transform ion mobility spectrometry (HT-IMS) [17,18] both of which requires no physical instrument modifications of instruments.…”

“…The use of HT in ion mobility spectrometry is presented independently by Clowers et al [18] and Szumlas et al [17]. Similar to HT-TOFMS, the BNG is modulated by a series of open and close pulses (maximum-length pseudorandom sequence), producing many ion packets that intermix in the drift region.…”