Another important point to consider when preparing your samples for NMR analysis is the tube quality. Compared to traditional high-field NMR instruments (1H operating frequencies > 300 MHz), low-field spectrometers can use lower quality NMR tubes and still obtain good spectra. However, using too poor of a tube will always result in poor spectra, no matter the field strength. To achieve good spectra, ensure that the tube is straight (camber) and that the inner (ID) or outer (OD) diameters are relatively parallel to one another (concentricity).5 Note that camber is the measure of the lack of straightness and concentricity is the largest variation of the wall thickness of an NMR tube.5 You can get these numbers from your tube provider and most of them will also recommend to you specific tubes that cater to the magnet strength that you intend on using. Furthermore, if the NMR tubes selected are sufficient for spectrometers with a 1H operating frequencies of 100 MHz or above, then it is very likely the quality of the tube is sufficient for use with our instruments.
During the preparation of your NMR sample, focus should be placed on the elimination of solid particles and the quality of the NMR tube to optimize the quality of your NMR spectrum. This can reduce spectral artifacts, line broadening, and improve reliability. By using the techniques mentioned above, you will be rewarded with spectra that are easier to interpret, thus providing you with more useful information.
Please feel free to contact us regarding the preparation of NMR samples or to ask us questions about how this can benefit your chemical applications.