The instruments in the Chemistry Department NMR Laboratory are available for use by “Qualified Operators” in accord with time constraints posted for each instrument. In general, use is restricted to shorter time slots during prime time hours (09:00 to 18:00) with longer experiments performed at off peak hours as much as possible. The management reserves the authority to make exceptions to this policy when it its judgment, it is necessary or desirable to do so. Exceptions to this policy must be approved by the director of the facility, Dr. Stephen Lynch.

Operators

     Qualified Operators are persons who have received instruction from a TA (initial instruction is normally done by one of the NMR TAs, and then have successfully completed a check out on the instrument with Dr. Lynch at which time the user will be given his/her own account. Before being awarded his/her own account, a user can use an instrument with help from a member of their lab; however, the lab member must be present. All users will be checked-out on the Inova 300 or VNMRS400 first in order to become acquainted with the software; users will then be given accounts to all instruments except the Inova 600. Access to the Inova 600 requires Tuning training and a reason to use the 600- generally, higher H1 signal to noise, better resolution, 2D experiments, or high molecular weight molecules. The check out involves demonstrating the ability to use the instrument properly, including changing samples, finding the deuterium lock signal by adjusting the Z0 offset and ‘locking’ on that signal, adjusting the lock power, lock gain and lock phase; adjusting shims to obtain satisfactory resolution; setting a reference signal. The user will then follow correct log out procedure. When this is successfully completed, the operator will be given an account and password on the instrument and a permission to card access to the NMR Lab (17A, 18A, 18B). Passwords are not to be shared with others who have not yet become qualified operators. However, qualified operators are encouraged to assist operators who are not yet qualified by logging in for them and being available to help them if needed.

NMR tubes – Sample Volume

     The probes on superconducting magnets have close tolerances and are sensitive to NMR tube quality and sample volume. Higher quality tubes should be used for higher quality spectra. The so-called Disposable tubes can be sufficiently out of tolerance to give poor quality spectra. Tubes heated above 100 degrees in a drying oven may become warped or bent, which will also give lower quality spectra. There is a high probability of spinning side bands or other spectral degradation with these tubes and with overheated tubes which have become warped. For routine work, it is suggested to use tubes of a quality at least equal to 507PP tubes (5mm od). For best results with critical samples (2D or NOE experiments) tubes of quality equal to or better than 528PP are recommended, but at least 507pp. Tubes that are 7” long are OK in all systems. Longer tubes may be desirable if the tube is to be sealed off in a flame. Tubes with chipped or cracked edges constitute a safety hazard and should not be used. Tubes shorter than 6 ¼” should not be used. A filtered volume of 0.7 ml is recommended for 5 mm tubes for routine work, or 0.5 ml for low concentration samples. Smaller volumes require much more adjustment of shims and can easily take more time to shim than to collect the data. The absolute minimum volume is 0.4 ml, but shimming will be difficult. If your sample concentration is very low, it is suggested to use a Shigemi NMR tube with a matched solvent.

Logbooks / Problems

     All the instruments have accounting software that maintains a chronological log of instrument use. In addition the systems have paper logbooks. Users are requested to enter their name, research group, start and finish times, nucleus, and temperature if other than ambient temperature was used. If problems are encountered, a description of the problem should be entered in this logbook. It is helpful to NMR personnel to be able to contact persons who have experienced a problem in order to know what needs to be fixed. For urgent problems, call Dr. Stephen Lynch or one of the TAs. For less urgent issues, write the issue in the logbook and email Dr. Stephen Lynch and/or the TAs.

Saving / Archiving Data

     Files may be saved in your home directory on any instrument. The data will be there as long as you are at the university. Data should be transferred to your computer for processing with MestreNova and for archiving. 

Logout / Stand-by Conditions

     Before logout, operators should return the instrument to standard conditions for proton acquisition in CDCl3 solvent with the deuterium lock engaged and shims set for the standard sample. This is especially important if you have used a solvent other than CDCl3.

     On the NMR systems it is important that all acquisitions be halted (“aa”) and the vnmr program be exited by typing “exit” in the command line then logout of the computer.  

Accidents

     Be very careful inserting and removing sample tubes in the spinner turbines to avoid loss of important samples and possible cut hands. The tubes have very thin walls and are easily broken. In the event a reference sample is broken (outside the probe) please leave a message for the TA or Lab Manager so that the sample may be replaced. If any sample gets broken (outside the probe) please clean up in an appropriate manner for the material and dispose of the broken glass and sample in proper places. If an injury results, it must be reported appropriately.

     If any sample gets broken in the probe, it is important to the performance of the NMR to get it cleaned up as quickly as possible. Notify Dr. Stephen Lynch and the NMR TAs by phone or in person. The sooner the matter is addressed the less likely there will be permanent damage. For samples broken in the probe please leave a note on the instrument keyboard warning users not to use the instrument. The minimum information needed for clean-up: name and structure of compound if known, or at least class of compound, name of solvent, toxicity of material, other solvents which dissolve it, special precautions in handling it if toxic. This is important for those of us who will need to clean it out and for the probe shop if we have to send the probe for repair.