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I'm using Bruker Avance 300 spectrometer (Topspin processing software). When using "RGA" GR value jumps up to 3000 and more not depending on sample concentration. When RG is set manually spectra 1H spectra still looks little distorted. What could be causing this error???How it can be fixed?

asked Apr 11 '14 at 04:04

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Please elaborate on the type of samples and experiments that you are doing. - Kirk Marat (Apr 14 '14 at 07:25)

Perhaps send me same sameple data (kirk.marat@umanitoba.ca) and I can give you some advise. - Kirk Marat (Apr 14 '14 at 07:27)

3 Answers:
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From my experience, if the S/N is poor, or if the lines are very broad, RGA will give nonsensical values. This may or may not be your problem as my experience is mainly with solid-state NMR machines with samples that have much broader linewidths.

For checking whether the RG is set too high, look at the FID as the start of the experiment as it is acquiring and see if the top and bottom looks horizontal (cut off), if it is then it is too high and will give you distortions, as shown on this page written by Glenn Facey of University of Ottawa: http://u-of-o-nmr-facility.blogspot.ca/2007/10/consequences-of-setting-receiver-gain.html Unfortunately you can only see this at the beginning of the experiment as once you have acquired a few more scans the distortions in the FID look as if they are smoothed out but will still give you a distorted spectrum.

The solution, as apophis said, is to set it manually. This page (also by Glenn Facey) explains how S/N can vary with RG. You should vary the value of RG manually, trying several different values, and find a maximum that gives good S/N without distortions. http://u-of-o-nmr-facility.blogspot.co.uk/2013/02/receiver-gain-and-signal-to-noise-ratio.html


answered Apr 14 '14 at 07:10

Ying's gravatar image


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Unless your sample is extremely strong you could set a fixed RG and leave it. Alternatively, you could perform an RGA but add a line in your AU program to put a maximum value. In my studies, a receiver gain of more than 128 does almost nothing for signal to noise and can cause peak distortion problems (and bad baselines). Try:

float myrg;
if (myrg>128) myrg=128;

answered Sep 10 '14 at 04:07

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John Hollerton

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I also had this problem many times. Unfortunately i can not give u a good explanation for this problem but it is bruker, very shitty stuff. Just decrease the rg manually to a proper val (~500) your spec may look better. Hope this may help u.


answered Apr 12 '14 at 17:23

apophis's gravatar image


I have both Avance and Avance III systems, used for both liquids and solids, and have never really had much problem with RGA. For solids with very wide SW I do tend to set the RG manually. If it is too high, there will be an ADC overload error message. - Kirk Marat (Apr 14 '14 at 07:25)

Our AV 300 with BACS 60 sample changer runs continuously in automation, and runs RGA on every spectrum - never had a bad spectrum due to an RGA problem,. - Kirk Marat (Apr 16 '14 at 12:50)

This is correct, what Kirk Marat mentioned! I got problems, doing RGA with solid state samples ... ADC overload error! With RGA it is fine on the liquid samples. - Ulrich Haunz (May 05 '14 at 02:20)

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Asked: Apr 11 '14 at 04:04

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Last updated: Sep 10 '14 at 04:07

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