The signal-to-noise ratio in an NMR spectrum can be affected drastically the choice of the receiver gain setting, so care should be taken to set the receiver gain correctly for optimum results. At very low receiver gain settings, both the signal and the noise use only a fraction of the available digitization levels of the analog-to-digital concertor (ADC). As a result, the intensity of each point in the FID is represented with only a few possible values and the FID is "choppy". This is analogous to a black and white photograph being represented with a coarse gray scale of only a few shades of gray. Just like such a poorly represented photograph, the NMR spectrum contains a great deal of digital noise and therefore a low signal-to-noise ratio. As the receiver gain is increased, the FID is digitized with more available digitization levels. Since the thermal noise in the FID at low receiver gain settings is smaller than or comaparable the size of the digitization step of the ADC, the noise (unlike the signal) will not be amplified by increasing the receiver gain until it exceeds the size of the digitization step of the ADC after which it will be amplified in the same way as the signal. As a result, the signal increases more so than the noise as the receiver gain setting is increased therefore, the signal-to-noise ratio in the NMR spectrum increases steadily as the receiver gain setting is increased. As the receiver gain is increased beyond the point where the thermal noise exceeds the size of the digitization step, both the sginal and the noise can be digitized properly and the signal-to-noise ratio increases much less as a function of receiver gain setting increase. If the receiver gain is increased too much, the signal will exceed the limits of the ADC, the FID will be clipped at the beginning and the NMR spectrum will be severely distorted. The first figure below shows a series of spectra plotted as a function of the receiver gain setting. The spectra were scaled such that the signals were all of the same height. It is clear that the signal-to-noise ratio increases initially and then levels off. The data are plotted in the second figure.
[U. of Ottawa NMR Facility Blog] NMR Tube Thickness and Signal-to-Noise-Ratio
NMR Tube Thickness and Signal-to-Noise-Ratio
The amount of NMR signal is expected to be proportional to the amount of sample inside the coil of the NMR probe. As a result, the signal-to-noise ratio for samples run in NMR tubes with thick walls is expected to be lower than that for comparable samples run in NMR tubes with thinner walls due to a reduced filling factor of the NMR probe coil. I was curious to see how much of a difference in signal-to-noise ratio there would be. 0.68 mL of CDCl3 (99.8 % D) was put in 5 mm NMR tubes with wall thicknesses of 0.38 mm and 0.80 mm. The NMR...
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12-08-2012 02:48 AM
Low concentration of a Gd-chelate increases the signal-to-noise ratio in fast pulsing BEST experiments
Low concentration of a Gd-chelate increases the signal-to-noise ratio in fast pulsing BEST experiments
Publication year: 2012
Source:Journal of Magnetic Resonance</br>
Nathalie Sibille, Gaëtan Bellot, Jing Wang, Hélène Déméné</br>
Despite numerous developments in the past few years that aim to increase the sensitivity of NMR multidimensional experiments, NMR spectroscopy still suffers from intrinsic low sensitivity. In this report, we show that the combination of two developments in the field, the Band-selective Excitation Short-Transient (BEST) experiment and the...
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08-08-2012 07:16 PM
[Question from NMRWiki Q&A forum] Pt 195 NMR Signal to Noise
Pt 195 NMR Signal to Noise
I need help with parameters on a Varian system for Pt-195 NMR. I am having trouble with signal to noise. From what I've read the sensitivity should be better than carbon but I'm not seeing that at all. Any suggestions?
Check if somebody has answered this question on NMRWiki QA forum
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05-04-2012 11:06 AM
[NMRpipe Yahoo group] Re: Signal-to-noise estimation
Re: Signal-to-noise estimation
Greetings, Dear Pipers, and Happy Winter Holidays, or Whatever ... There are lots of ways this could be done, depending on how rigorous you want to be, how
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12-25-2011 10:35 PM
[NMRpipe Yahoo group] Signal-to-noise estimation
Signal-to-noise estimation
Hello! I am new in "NMR world". I have some basic questions regarding the NMRPipe. I would like to know if there is a manner to estimate the signal-to-noise
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12-25-2011 10:35 PM
[Question from NMRWiki Q&A forum] poor signal to noise on 1H-15N heteronculear NOE
poor signal to noise on 1H-15N heteronculear NOE
I have recently attempted to run a 1H-15N heteronuclear NOE experiment in vnmrj (700 rt probe) using the standard sequence that comes with biopack, the signal to nose im getting compared to my standard HSQC is significantly reduced, is this normal? I do not recall this being the case when I ran this previously on a bruker 600 with RT probe? is this normal or does this suggest something is miss set? Also in the no NOE experiment I get very broad noise in the centre of my spectrum/water line.
regards
Tom
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11-01-2011 01:52 AM
Signal enhancement in protein NMR using the spin-noise tuning optimum
Signal enhancement in protein NMR using the spin-noise tuning optimum
Abstract We have assessed the potential of an alternative probe tuning strategy based on the spin-noise response for application in common high-resolution multi-dimensional biomolecular NMR experiments with water signal suppression on aqueous and salty samples. The method requires the adjustment of the optimal tuning condition, which may be offset by several 100 kHz from the conventional tuning settings using the noise response of the water protons as an indicator. Although the radio frequency-pulse durations are...