Service Spectroscopy

Service Spectroscopy

NMRFAM is available for service spectroscopy. By our mandate from the NIH, service spectroscopy are any projects that are not core projects nor collaborative projects. These experiments are done on facility equipment with facility personnel acting in an advisory capacity if necessary.

In addition, there is some capability for routine service spectroscopy. This occurs on the standard “service spectroscopy days” of Tuesday and Thursday afternoons on pisa, the DMX-400. Samples are run from 1 pm until 5 pm and usually only routine ¹H and high sample concentration ¹³C or ³¹P can be run. The heteronuclear samples are usually run only after the ¹H spectra have been acquired. When data is collected with the assistance of a staff member, users are charged $50/hour plus the per hour fee for spectrometer time.

In addition to simple 1D experiments (which can include solvent suppression and decoupling), any of the DEPT experiments can be run, and many 2D experiments can be run (COSY, TOCSY, ROESY, HMQC, HMBC). Since these are experiments require more time for completion, they would be run after the more typical 1D experiments. If there are too many 1D samples, it is therefore possible that the experiments might be postponed until a later time.

Steps to Getting a Service Run

1. Fill out  a service time request form.
2. Properly prepare your sample!
   • Make sure your sample is “clean”!
   • Make sure your tube is clean! None of us need to see another “reference spectrum” of acetone.
     • Cleaning the tube in HNO₃ is good. It tends to remove metal contaminents.
     • Even new tubes should be cleaned, especially if you have a dilute sample.
     • Avoid stop-cock grease contamination, especially if you have peaks near 0 ppm.
   • Use the right amount of sample. As the molecular weight of your sample increases, use the higher range of the sample masses given below. The bottom end of the ranges works adequately for a sample of about 220 g/mole.
     • ¹H and ¹⁹F: about 0.2 - 10 mg
     • ¹³C: 10 - 50 mg
     • ³¹P: 2 - 20 mg
   • Solid material degrades spectral quality.
   • Gels are a bad idea also.
   • Too much sample gives a poor quality spectrum.
   • Use a deuterated solvent.
     • Don’t use an “old” solvent. Old bottles are often contaminated with water or other compounds. DMSO is very good at picking up contaminants. In the case of CDCl₃, there is the strong possibility of HCl being present in the bottle.
     • Remember to lyophilize your sample against D₂O if you’re trying to obtain a ¹H sample that may have small peaks in the vicinity of the water peak. This assumes that such peaks are NOT exchangable with the solvent.
   • Don’t add TMS nor use a solvent with added TMS. The best option is to either pipette some vapor from the TMS bottle into your sample or to add a drop of solvent with 1% TMS.
   • Don’t make too small of a sample. 0.50 ml is fine. If you have multiple samples, make them all the same volume!
   • Don’t make a sample with more than 0.60 ml. You’re just wasting money on expensive deuterated solvents.
3. Bring the sample(s) by the NMR Facility by 2 pm Tuesday or Thursday to have a good probability of getting your sample run that day.
4. Make sure the service spectroscopist understands what you need for spectra!
5. Remember that ¹H and ¹⁹F service takes priority over ¹³C and ³¹P service.

When in doubt, ASK FOR ADVICE!