Hadamard transform spectrometry

S.A. Dyer, Tutorial Hadamard transform spectrometry. Chemom. Intell. Lab. Syst., 12 (1991) 101-115. 

Infrared spectra may also be obtained by two other relatively new techniques, Fourier or Hadamard transform spectrometry. The Fourier method utilizes a Michelson... 

Plankey et al have reported on the application of Hadamard transform spectrometry to the ultraviolet and visible spectral regions. The Hadamard technique utilizes the dispersed radiation from a conventional spectrometer. The radiation is passed through a coded mask, recombined, and recorded. The mask is composed of N slits, and N measurements are made with the mask in different positions. After measurement, N simultaneous equations must be solved with a Hadamard matrix to obtain the spectrum. The mask must be moved mechanically and reproducibly and a computer is used to solve the simultaneous equations. 

J, A. Decker "Hadamard Transform Spectrometry a New Analytical Technique," Anal. Chem. 46 (1974) 1803. 

Decker Jr., J. A., Hadamard-Transform Spectrometry. New Analytical Technique , Anal. Chem. 1972, 44, 127A-134A. 

In ToF-MS, the ion source is pulsed to create packets of ions. In the conventional procedure, the system waits for all the ions in a packet to reach the detector before injecting the next packet of ions. Complications arise when ToF-MS is coupled to a continuous ion source. Such coupling is therefore often accomplished by the orthogonal extraction approach, in which a segment of the ion stream is accelerated orthogonally by a push-out pulse. However, in this process, up to 95 % of the information contained in the ion steam is lost. Recently, Hadamard transform time-of-flight mass spectrometry (HT-ToFMS) was developed to couple continuous ion... 

Non-dispersive multiplex spectrometers include Hadamard transformation spectrometers and Fourier transform spectrometers and are particularly useful for the case of very stable sources. In both cases the information, such as intensities at various wavelengths, is coded by a multiplex system, so that it can be recorded with a conventional detector. A suitable transformation is then used to reconstruct the wavelength dependence of the information. In Hadamard spectrometry use is made of a codation of the spectrum produced by recombining the information with the aid of a slit mask which is moved along the spectrum [66],... 

Brock, A., Rodriguez, N., and Zare, R.N. (1998) Hadamard transform time of flight mass spectrometry. Anal. Chem., 70, 3735-3741. 

Fig. 18. Schematic of the chemical mapping instrumentation in the Mid- and Near-IR Spectral Regions by Hadamard Transform/FT-IR Spectrometry. (Reproduced from [ 126])...

Hadamard. Hadamard-transform NIR spectrometry (see Fig. 4.1.15) (HT-NIR) is based on the combination of multiplexing and dispersive spectrometers where the... 

Zare, R. N. Fernandez, F. W. Kimmel, J. R., Hadamard Transform Time-of-Flight Mass Spectrometry More Signal, More of the Time , Angew. Chem. 2003, 42, 30-35. 

The main drawback with IMS is its inherently poor selectivity. As with GC, many compounds cannot be fully separated by IMS, and even if they are separated it may not be easy to establish their identities. To try and rectify this, IMS has been coupled with mass spectrometry [6], but this comes at the expense of increased cost, complexity and size of the instrument. A notable development is Hadamard transform IMS [7,8], which promises to resolve the problem of the low duty cycle of conventional IMS and should therefore result eventually in a significantly improved sensitivity, although again this delivers a more complex instmment. 

J. A. De Haseth, Fourier Transform Infrared Spectrometry, p 387 in Fourier, Hadamard and Hilbert Transformation in Chemistry (A. G. Marshall, ed.) Plenum, New York, 1982. 

A. deHaseth, "Fourier Transform Infrared Spectrometry", Ch. p. 387 in Fourier, Hadamard and Hilbert Transformations in Chemistry, ed. A.G. Marshall (Plenum Pubi. Corp., 1982). 

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