Coaxial Inserts For NMR Sample Tubes
A coaxial insert consists of an upper glass alignment tube with a precise outer diameter that fits very closely within the matching 5mm or 10mm thin wall outer glass NMR tube, ensuring accurate coaxiality and centering of the insert within the outer NMR tube.
The lower glass stem tube, of a smaller diameter, typically holds an external lock or reference material. The smaller diameter stem tube is precision sealed to the upper alignment tube using a highly accurate, state-of-the-art glass working lathe, maintaining the coaxial alignment necessary for the acquisition of high-quality spectra.
The accompanying table presents the most commonly used sizes for Bruker and Varian probes. Please note that the last two inserts listed in the table are constructed from quartz glass, whereas the remaining inserts are made from low expansion borosilicate glass (Pyrex® or equivalent ASTM Type 1 Class A glass).
The data in the columns under “Stem Specifications” lists the stem tube outer diameter, length and the volumetric capacity of the stem tube when the entire length is filled (either 50mm or 60mm).
The last column of the table gives the volumetric sample capacity remaining within the outer 5mm or 10mm NMR tube when the coaxial insert is positioned to full depth within the outer tube, as measured to the top of the insert stem tube (again either 50mm or 60mm).
All inserts are made to an overall length of 206mm (8-1/8”) and include a cap for the insert tube along with a special cap to seal the insert to the top of the outer NMR tube.
As always, we would be delighted to quote on custom requests for stem diameters and lengths not given in the accompanying table.