It is well known that large background signals dominate the baseline of spectra from nuclei such as 19F and 11B.\u00a0 Most of these arise from solid material that is used in the construction of the probe electronics or in the case of 11B, from the NMR tube material itself.<\/p>\n
The typical appearnace of these distortinos are in the form of wide humps that appear like ‘hills’\u00a0\u00a0 that are tens of ppm broad.\u00a0\u00a0\u00a0 Irrespective of the origin of these distortions, the signature of these on the time domain signal i.e. FID is predicatable i.e. large spike like appearance for the first few points of the digitized FID signal.\u00a0 A simple processing technique called ‘backward linear prediction’\u00a0\u00a0 can be effectively used to remove baseline distortions caused by these artifacts.<\/p>\n
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The good news is that, there is an in-built Topspin automation command that can automagically remove the baseline distortion for you and it uses this very same linear prediction algorithm !\u00a0 <\/strong><\/p>\n On the GG500 instrument with 19F-optimized iProbe, you can do either of the following to get perfectly flat baselines with 19F<\/p>\n In either of these methods, the script will copy the existing raw data to an unused Exp no. : 100001 (highly unlikely that you would have used this number already). It will then process the data, applying backward linear prediction to give a perfectly flat line.<\/p>\n _______________________________________________________________________________________<\/p>\n Here is some visual guidance, when you attempt this at the instrument :<\/p>\n BEFORE<\/strong> cryoproc1d<\/strong>\u00a0 the file <\/em>browser looks like this :<\/p>\n WHEN you run cryoproc1d<\/em><\/strong> you will get this warning message, that you can simply acknowledge :<\/p>\nGG500 :<\/h3>\n
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