We have recently seen some researchers producing poor data by using cheap, unlabeled NMR tubes. I am therefore reposting our instructions regarding the use of NMR tubes here:
The only way to obtain useful data is to have well prepared samples in high quality nmr tubes. Do not buy nmr tubes in bulk packets that do not have labels specifying what they are. You will not know the quality of these tubes. At the minimum you will get poor results and the worst they will damage the nmr instruments There are many grades of nmr tubes. Below is a list of nmr tubes that we found to work well for our instruments Quality nmr tubes from other vendors might work as well; we are happy to help testing these tubes.
For instruments of 500 MHz and less.
Norell (nmrtubes.com) 507-HP-7 (these are sold in the VWR stockroom)
Wilmad (willmad-labglass.com) 527-PP-7
New Era (https://newera-spectro.com) NE-HP5
For instruments of 700 MHz and 800 MHz you can use the tubes above but you will get better results from tubes that are specified for those field strengths.