At the moment our laboratory would like to buy portable NMR spectrometer and we would like to see some real not promo spectrograms. Could those who constantly work with such devices share spectra (indicating the brand and year of manufacture of your device) and feedback on working with them?
The vendors' systems have all of the specifications that you need to know whether the system is capable of giving decent data for your samples.
The operating field of the instrument will give you a good idea of its ability to disperse signals. 60MHz will be fine for very small molecules but will not be suitable for complex molecules (or those with strongly overlapped signals).
The other parameter is the signal to noise. If you are looking at 300 mw compounds and you have less than a mg of material, you will be unlikely to get anything useful.
The last thing to watch for is stability. Permanent magnets are highly sensitive to temperature variations. When you say "portable", you can pick them up and move them (if you are strong) but they will take a long time to stabilise!
Article Benchtop NMR analysis of piperazine-based drugs hyperpolaris...
The guys at Manchester met (MMU) have an Oxford instruments bench top NMR.
The supplementary for this paper (free) has examples. They have published other papers featuring it as well.
best P
Patrick Killoran good reference! The supplementary data showing the spectra of simple piperazines at 60MHz shows some of the limitations of benchtop instruments. These are simple molecules with well-dispersed signals but one would struggle to make any structural assignments unless using a priori knowledge about the molecules. The article doesn't mention the sample concentration in these spectra but I suspect that there is a quite a lot of material.
There are situations where a benchtop system will be fine to perform a role but it will never be the general purpose workhorse that a decent higher field instrument is.
I started my NMR career at 60MHz and I know that a lot of work was using precedence, lanthanide shift reagents, and intuition. Unlike these old CW instruments, modern benchtops have the advantage of being FT, giving access to improved signal to noise and 2D experiments. That said, I still wouldn't want to go back to 60MHz!
John Hollerton I agree, higher field all the way if you can! The link below suggests 50mg/mL for ibuprofen, they also have examples at differing numbers of scans. As you mentioned, it depends on the intended application (I could see it working well for process development).
Best Paddy
Attallah Sheat
https://www.nanalysis.com/will-60mhz-work-for-you
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