Traditionally, sample sizes are 3-5 times the height of the probe R f coil. All magnetic field distortions caused by susceptibility discontinuities at the upper air-sample and lower glass-sample interfaces were far from the sensitive probe R f coil region. Small samples diluted to larger traditional volumes (1 mL) yield poor NMR spectra in high field spectrometers.
Through magnetic susceptibility matching of the sample solvent, Doty Plugs allow the sample to be substantially concentrated by extending out the air-sample / glass-sample interfaces far enough away from the R f coil region to remove these field distortions.
Plugs sold in sets of two. Positioning Rod and Collar also a set and ordered separately. The upper face of both plugs has a thread to firmly attach a positioning rod which holds the upper plug in place. In turn, the rod is held by a collar that rests on the top of the tube. A special sealing collar (equipped with two o-rings) may be ordered separately for long term storage of samples where solvent evaporation can alter results (replaces standard collar).
Advantages of Doty Susceptibility Plugs
-Match a wider range of solvents
-Less fragile in variable temperature experiments involving freeze-pump-thaw
-Use with our 3, 5 or 8 mm thin wall tubes
-Easy sample loading and cleaning
-Fully compatible with Bruker , Agilent (formerly Varian) and JEOL spectrometer/probe
-Designed for easier air bubble removal. Product numbers that include a "V" have vent grooves along the outer surface for this and use with viscous samples/solvents
-May be removed from the sample tube with minimal sample loss (1-2 percentage) after spectra are obtained, then used with other samples
Tips to Consider when Selecting and Using Doty Plugs
- Determine the sample solvent. Note: See above regarding viscous samples/solvents.
- Select plug material with the closest match of magnetic susceptibility constants. Density of plugs must be greater than density of sample-solvent.
- Check chemical resistance compatibility with sample/solvent.
- Ensure solid-state wideline background from nuclei in plug material does not interfere with analysis.
- Keep Doty Plugs in deuterated solvents after usage to suppress water absorption from the atmosphere.
- Determine plug length with a depth gauge; ideally plugs should not protrude into the R f coil limit.
Susceptibility constants of rod/collar are inconsequential; material selection is based on chemical resistance. G-10 rods are more rigid and easier to use; Kel-F rods are recommended for use with organic solvents.
Note: L = Bottom Height (measured from the bottom of the tube to the bottom of the sample). Length should be chosen to most closely match your probe coil.
Plugs are sold as sets of two. Positioning rod and collar are also sold as a set and ordered seperately. For long term storage of samples where solvent evaporation is a problem, our sealing collar is ordered separately and replaces the standard collar supplied with the rod.
Please choose length of bottom plug that most closely matches your probe coil.
Product numbers that include "V" have vent grooves along outer surface for use with viscous materials.