Why does one brand of NMR tubes fit differently into my spinner turbine than another brand?

Some brands of NMR tubes have outside diameter variations that present problems when loading sample into a spinner turbine, such that serious damage will occur to the NMR probe. Special care must be taken with stringent attention to quality control when monitoring NMR tube production, so that outside diameter variations are held to a minimum. In Norell’s manufacturing process, with the use of state-of-the-art equipment, NMR tube outside diameter variations are held to extreme minimums.

Keep in mind that spinner turbine o-rings can be worn out too and need replacing. From field tests we have found that spinner turbines also vary considerably in bore inside diameter and are not not manufactured as precise as glass NMR tubes. It is therefore recommended to service spinner turbines periodically along with replacement of the o-rings.