Reference deconvolution

The reference deconvolution procedure is not limited to addressing lineshape distortions in ID spectra, having a number of potential applications in high-resolution NMR spectroscopy [53, 54] and has been shown to be effective in improving NOE difference spectra [52], for ti noise reduction in 2D spectra [56, 57] and in the production of high-resolution diffusion-ordered spectroscopy (DOSY) [58]. 

---

Reference Deconvolution, Phase Correction and Line Listing of NMR Spectra by the ID Filter Diagonalization Method. 

Fig. 2. (a) Raw 300 MHz proton spectrum of a mixture of acetone and ethanol in deuteri-ochloroform (b) after reference deconvolution using the acetone signal as reference and an ideal lineshape of a 1 Hz wide Lorentzian and (c) after reference deconvolution with an ideal lineshape characterized by a negative Lorentzian width of 0.1 Hz and a Gaussian width of 0.4 Hz. The 0.1 Hz Lorentzian term represents the approximate difference in natural linewidth between the ethanol and acetone signals, and is responsible for the wings on... 

Fig. 3. (a) 300 MHz proton spectrum of the molecule shown, and (b) 500-fold expanded NOE difference spectrum obtained using reference deconvolution to enforce identical reference lineshapes (2 Hz Lorentzian) for the chloroform signals in the irradiated and unirradiated spectra. Note the complete absence of the usual up-down difference artefacts in trace (b), even for the sharp singlet methyl signals the remaining artefacts are largely homodecoupler... 

The use of reference deconvolution for the correction of artefacts in nuclear Overhauser effect difference spectroscopy [9] is illustrated by the spectra of fig. 3. The experimental technique used here differs slightly from that normally encountered in using a control spectrum in which the preirradiation is gated off rather than shifted in frequency, and in keeping the decoupler and transmitter at the same frequency. These modifications were... 

Fig. 4. (a) Conventional 500 MHz HMBC spectrum of sucrose octaacetate in deuteriochlo-roform, and (b) HMBC spectrum with ti-noise corrected by reference deconvolution. (Reproduced, with permission, from Signal Treatment and Signal Analysis in NMR, ed. D.N. Rutledge, Elsevier, Amsterdam, 1996)... 

Reference deconvolution is unusual among data processing methods in using internal evidence to repair the damage done to the spectral data by instrumental imperfections parenthetically, it may be noted that the form of the correction function R t) itself can be a useful guide to instrumental fault-finding. The principal uses of reference deconvolution are in the pro-... 

One method of reducing the effects of the line-broadening due to the z-gradient present during data acquisition is to use reference deconvolution ... 

The process of reference deconvolution [14] can be described mathematically as follows ... 

Figure 8.2.7 Reference deconvolution applied to the methanol peak (a) original peak (b) methanol peak deconvolved to a 2 Hz Lorenzian lineshape (c) gradient-shifted methanol peak (d) gradient-shifted methanol peak deconvolved to the same 2 Hz Lorenzian lineshape (e) comparison of the sub-spectrum of the methanol sample using the subtraction algorithm with (sharp peak) and without (flattened peak) reference deconvolution. Reprinted from Hou, T., MacNamara, E. and Raftery, D., NMR analysis of multiple samples using parallel coils improved performance using reference deconvolution and multi-dimensional methods , Anal. Chem. Acta, 400, 297-305, copyright (1999), with permission of Elsevier Science...

The application of the reference deconvolution technique to overcome the effect of magnetic field inhomogeneity in high-resolution NMR has recently been reviewed by Metz et al.21 In this technique, the observed resonance lineshape from a single resonance line is used to deconvolve the observed lineshapes to produce the Lorentzian lineshapes associated with liquid samples. 

---