Increasing NMR signal sensitivity of samples containing high salt concentration

A supplementary solution for increasing NMR signal sensitivity of samples containing high salt concentration, by reducing back ground signal noise.

There is a great article by Alexander E. Kelly, Horng D. Ou, Richard Withers, and Volker Dötsch titled “Low-Conductivity Buffers for High-Sensitivity NMR Measurements”, J. Am. Chem. Soc., 124 (40), 12013 -12019, 2002. 10.1021/ja026121b S0002-7863(02)06121-8 Web Release Date: September 13, 2002 Copyright © 2002 American Chemical Society , that demonstrates that salt concentration alone is not the decisive factor in controlling background noise levels created by high salt matrixes, but that concentration and ion mobility together need to be considered in reducing noise levels.

Many researchers have approached us with the need to have less sample volume, after adjusting to a new buffer, to take advantage of this effect. For changing sample volume, we are offering our customers several solutions. One option is to use our 5mm thick walled (1.4mm wall) NMR tube, which has a 0.19ml fill volume compared to the 0.71ml fill volume of our standard 0.38mm wall tube at 50 mm sample height. The second option involves using a new special spinner insert adaptor that holds either 4.25mm, 4.00mm, 3.00mm, 2.50mm, 2.00mm, 1.70mm, and 1.00mm NMR tubes in a 5mm spinner turbine. We have adaptors for both stock Bruker and Varian spinner turbines, and good NMR signal has been reported even when using a 1mm NMR tube with a 5mm cryo-probe. The advantage of using the Norell spinner insert, is that you do not need to purchase or have specially made spinners for the complete selection of NMR tube sizes. You can now determine very easily the tube size that performs optimally for the type of sample and sample volume that is called for in the experiment.

Call the Norell customer service department for more details on how to use the new inserts.

Molar concentrations and volume calculations in NMR tubes

We recently had a student ask us about molar concentrations and volume calculations in NMR tubes, so we thought that the following example could possibly help out other students having similar problems. In the original question, the student asked for the molar and mass concentrations of a 25k Daulton protein, of which 2.5 mg were dissolved in 1 liter of water. We wrote the solution out in pen, because it was easier to read. Click the link below to view.

http://www.nmrtubes.com/blog/121506_formula.jpg

What type of ESR sample tube to purchase?

We recently had a grad student ask us what type of ESR sample tube to purchase. He was performing a quantitative experiment involving a metal complex dissolved in toluene. The point of the experiment was to study the interaction of various wavelengths of UV radiation upon the interaction of the metal complex. We recommended that precision Suprasil ESR tubes be used, primarily because the solvent height will remain the same between samples, which will keep the sensitivity of the cavity about the same. Also, the synthetic quartz can transmit wavelengths down to 190nm, which is what the experimenter required. Our recommendation was to use Norell Part No. S-4-EPRSQ-250P, a 4mm OD X 250 mm length precision ESR tube which is the typical size used in 4 or 5mm finger dewars.