Hadamard Transform Analytical Systems

Harwit, Martin

doi:10.1007/978-1-4684-2403-4_7

Cited by 43 publications

(72 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Figure 3A shows the encoding sequence used for the multiplexed IMS-TOF MS experiments. The important difference between this sequence and the conventional encoding sequences used in HT photospectrometry, 20 HT-TOF MS, 25 HT-CE 24 and HT-IMS 27 is that the adjacent digital `1' events (i.e., "gate open" events) in our sequence are separated by `0' events (i.e., "gate closed" events), while a typical encoding sequence in HT experiments has combinations of consecutive `1' events.…”

Section: Resultsmentioning

confidence: 99%

“…HT has been extensively used in optical spectrometry for over five decades. 20 The concept of measuring different bundles of objects by weighing them in groups rather than individually was first proposed by Fellgett, and the resulting increase in accuracy is sometimes called the Felgett or multiplex advantage. 21,22 If spectral line intensities are simultaneously detected in N measurements, the theoretical increase in SNR over a single measurement is then expected to be .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Multiplexed Ion Mobility Spectrometry-Orthogonal Time-of-Flight Mass Spectrometry

et al. 2007

View full text Add to dashboard Cite

Ion mobility spectrometry (IMS) coupled to orthogonal time-of-flight mass spectrometry (oTOF) has shown significant promise for the characterization of complex biological mixtures. The enormous complexity of biological samples (e.g. from proteomics) and the need for both biological and technical analysis replicates imposes major challenges for multidimensional separation platforms in regard to both sensitivity and sample throughput. A major attraction of the IMS-TOF MS platform is separation speeds exceeding that of conventional condensed-phase separations by orders of magnitude. Known limitations of the IMS-TOF MS platforms include the need for extensive signal averaging due to factors that include significant ion losses in the IMS-TOF interface and an ion utilization efficiency of less than ~1% with continuous ion sources (e.g. ESI). We have developed a new multiplexed ESI-IMS-TOF mass spectrometer that enables lossless ion transmission through the IMS-TOF as well as a utilization efficiency of >50% for ions from the ESI source. Initial results with a mixture of peptides show a ~10-fold increase in signalto-noise ratio with the multiplexed approach compared to a signal averaging approach, with no reduction in either IMS or TOF MS resolution.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Multiplexed Ion Mobility Spectrometry-Orthogonal Time-of-Flight Mass Spectrometry

et al. 2007

View full text Add to dashboard Cite

show abstract

“…PRS sequences were derived as described elsewhere. 20 A typical 6-bit PRS comprises a combination of digital '1' and '0' elements as follows:…”

Section: Signal Encoding and Detectionmentioning

confidence: 99%

“…One of the most promising multiplexing approaches that give rise to sensitivity enhancement for all species in the course of signal detection experiment is based on Hadamard transform (HT). 20 In general, if signals are simultaneously detected in N measurements characterized by the uncorrelated noise, the theoretical increase in SNR over a single measurement is expected to be . By modulating a continuous beam from the ESI source with a Bradbury-Nielsen gate in an atmospheric-pressure IMS instrument (without MS), up to 6-fold increase in sensitivity has recently been reported in HT-IMS measurements.…”

Section: Introductionmentioning

confidence: 99%

Dynamically Multiplexed Ion Mobility Time-of-Flight Mass Spectrometry

et al. 2008

View full text Add to dashboard Cite

Ion Mobility Spectrometry-Time-of-Flight Mass Spectrometry (IMS-TOFMS) has been increasingly used in analysis of complex biological samples. A major challenge is to transform IMS-TOFMS to a high-sensitivity high-throughput platform for e.g. proteomics applications. In this work, we have developed and integrated three advanced technologies, including efficient ion accumulation in the ion funnel trap prior to IMS separation, multiplexing (MP) of ion packet introduction into the IMS drift tube and signal detection with an analog-to-digital converter (ADC), into the IMS-TOFMS system for the high-throughput analysis of highly complex proteolytic digests of e.g. blood plasma. To better address variable sample complexity, we have developed and rigorously evaluated a novel dynamic MP approach that ensures correlation of the analyzer performance with an ion source function, and provides the improved dynamic range and sensitivity throughout the experiment. The MP IMS-TOF MS instrument has been shown to reliably detect peptides at a concentration of 1 nM in the presence of highly complex matrix, as well as to provide a three orders of magnitude dynamic range and a mass measurement accuracy of better than 5 ppm. When matched against human blood plasma database, the detected IMS-TOF features were found to yield ~ 700 unique peptide identifications at a false discovery rate (FDR) of ~ 7.5 %. Accounting for IMS information gave rise to a projected FDR of ~ 4 %. Signal reproducibility was found to be greater than 80 %, while the variations in the number of unique peptide identifications were < 15 %. A single sample analysis was completed in 15 min that constitutes almost an order of magnitude improvement compared to a more conventional LC-MS approach.

show abstract

“…Complete descriptions of the matrices used for encoding the ion beam and of the inverse Hadamard transform used to deconvolute the raw data are found in the work by Harwit et al [12,19] and Wilhelmi et al [20] Crucial to HT-TOFMS, and all other HT techniques, is consistency between the matrices used in the encoding and decoding steps. A data set x is encoded with an n x n simplex matrix, S n , yielding a convoluted data set z.…”

Section: Impulse Response Modelingmentioning

confidence: 99%

Effects of modulation defects on hadamard transform time-of-flight mass spectrometry (HT-TOFMS)

Kimmel

Fernández

Zare

2003

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

In any Hadamard multiplexing technique, discrepancies between the intended and the applied encoding sequences may reduce the intensity of real spectral features and create discrete, artificial signals. In our implementation of Hadamard transform time-of-flight mass spectrometry (HT-TOFMS), the encoding sequence is applied to the ion beam by means of an interleaved comb of wires (Bradbury-Nielson gate), which shutters the ion beam on and off. By isolating and exaggerating individual skewing effects in simulating the HT-TOFMS process, we determined the nature of errors that arise from various defects. In particular, we find that the most damaging defects are: mismatched voltages between the wire sets and the acceleration voltage of the instrument, which cause positive and negative peaks throughout mass spectra; insufficient deflection voltage, which reduces the intensity of real peaks and causes negative peaks that are spread across the entire mass range; and voltage errors as the wire sets return from their deflection voltage to their transmission value, which yield significant reductions in peak intensities, create artificial peaks throughout mass spectra, and broaden real peaks by causing positive peaks to grow in the bins adjacent to them. Because the magnitude of the modulation defects grows as the applied modulation voltage is increased, BradburyNielson gates with finer wire spacing, and hence stronger effective fields for a given applied voltage, were produced and installed. Operating at 10 to 15 V where errors in the electronics are essentially absent, the most finely spaced gate (100 m) yielded signal-to-noise ratios that were more than two times higher than those achieved with more widely spaced gates. As an alternative method for minimizing skewing effects, HT-TOFMS data were post processed using an exact knowledge of the modulation defects. Nonbinary matrices that mimic the actual encoding process were built by measuring voltage versus time traces and then translating these traces to transmission versus time. Use of these matrices in the deconvolution step led to marked improvements in spectral resolution but require full knowledge of the encoding defects. ( , photoacoustic depth profiling [8], and capillary electrophoresis [9 -11]. In each case, the motivation has been the inherent improvement in signal-to-noise ratio (SNR) offered by multiplexing the signal. In addition to its high SNR values, HT-TOFMS coupled to continuous ion sources offers a 50% duty cycle over any mass range with the potential of reaching 100% [3]. As a result of its high SNR and duty cycle, the spectral acquisition rates of HT-TOFMS are superior to conventional instruments.Spectral errors resulting from modulation defects have been described for Hadamard instruments that encode optical signals using machined masks [12] and stationary liquid crystals [7,8]. These authors have also developed mathematical correction schemes to compensate for the effects of systematic errors. Hanley [13] recently published a review describing the so...

show abstract

Hadamard Transform Analytical Systems

Cited by 43 publications

References 23 publications

Multiplexed Ion Mobility Spectrometry-Orthogonal Time-of-Flight Mass Spectrometry

Multiplexed Ion Mobility Spectrometry-Orthogonal Time-of-Flight Mass Spectrometry

Dynamically Multiplexed Ion Mobility Time-of-Flight Mass Spectrometry

Effects of modulation defects on hadamard transform time-of-flight mass spectrometry (HT-TOFMS)

Contact Info

Product

Resources

About