--- Richard K. Shoemaker, Ph.D. NMR Facility Director University of Colorado at Boulder _________________ Easy. Since the relaxation of O-17 is very fast you can scan very fast and get a good S/N in a very short time. (T1 of water is 10-20 ms, of organic oxygens under 1 ms) You could increase the temperature to get sharper signals. O-17 of water is strongly pH and Temperature dependent. Reference is water, but 1,4-dioxane is much more convenient and it has the same shift as water at 40 degrees Celsius (0 ppm). If you want to study molecules in water you might want to get rid of the water signal. I've done several studies on O-17, nat. abundance and enriched. You might want to check them out: 1. J. Lauterwein, J. Schulte, M. Schumacher and M. Cerny, Magn. Reson. Chem. 30, 312, (1992), “17O NMR Spectra of the 1,6-Anhydro--D-Hexopyranoses and Related Compounds. Determination of Configurational Effects on the Chemical Shifts.” 2. J. Schulte and J. Lauterwein, Magn. Reson. Chem., 30, 334, (1992), “Lanthanide-Induced Shifts in the 17O NMR Spectra of 1,6-Anhydro--D-hexopyranoses. Evidence for Tridentate Complexing.” 3. J. Schulte and J. Lauterwein, J. Magn Reson. Ser. A 101, 95, (1993), “Water Suppression in 17O NMR Spectroscopy.” 4. J. Schulte and J. Lauterwein, Magn. Reson. Chem., 34, 527, (1996), “Application of 17O Chemical Shift Substitution Parameters to D-Hexopyranoses.” 5. J. Schulte and J. Lauterwein, Magn. Reson. Chem., 34, 703, (1996), “2D 17O,1H Chemical Shift Correlation Spectroscopy.” 6. J. Schulte, J. Magn. Reson., 134, 168, (1998), “Sequential Inversion Recovery with RIDE Simultaneous Suppression of Two Solvent Signals in 17O NMR Spectroscopy.” Jürgen Schulte, Ph.D. ______________ Dear Roger, Water is (or at least was until IUPAC adopted a new system last year) the standard for 17O chemical shifts. Therefore, I doubt if anyone has measured its dependence on pH and temperature. … Roy Hoffman, Hebrew University ________________ Take D2O, it contains more O17 than normal H2O. Dr. Matthias Findeisen _______________ … The trick is to open up the sweep width, use a small data table size, and use a 90 degree pulse. You can collect thousands of transients in minutes. Have fun, Kenner Christensen Chemistry Department NMR Facility University of Arizona ____________ One problem that you could find is the probe signal ( oxygen signal from the borosilicate) JOE 8-) -- Jose R. Martinez-Ortiz joenmr_at_caribe.net San Juan, PR 00931-1352 ---------------- …the lines are so broad, it usually doesn't matter if there is a slight variance due to temp and pH. Of course, I run solid-state NMR. Gary Turner Spectral Data Services, Inc. Contract NMR Data Acquisition 818 Pioneer St. Used NMR equipment newsletter Champaign, IL 61820 phone : (217)352-7084 fax : (217)352-9748 e-mail :sdsnmr_at_sdsnmr.com __________ …Most of the stuff I've seen done with O-17 in water has to do with T2/linewidth changes rather than any chemical shift measurements (bound vs free water, exchange, etc.). Brevard and Granger show a spectrum with good S/N (50:1?) using 1000 transients, 90 degree pulse, and 0.1 second rep rate. They show a 80 Hz linewidth on a 90MHz instrument. Good Luck. Steven K. Silber ___________ . … pH will effect linewidth of the proton coupled resonance. The argument is that at a pH either higher than or lower than 7 the base or acid catalyzed exchange of protons allows for a narrowing of the line. My experience is that the linewidths vary from 80 to 60 hertz at 11.74T(500MHz). Paul Molitor U Illinois, Urbana-Champaign --------------- … if using dilute H20, can see the triplet from H coupling (too much exchange in bulk water to see it). … if you search with my name, might find some stuff from then. Dr. Herbert Schwartz --------------- …. I don't think temp or pH matter too much to just seeing a signal. You may need to use an anti-ringing sequence depending on your probe. I still use my trusty copy of "Handbook of High Resolution Multinuclear NMR" by Brevard and Granger (1981) when hunting a new nucleus. Regards, John Harwood _____________ …Set up the instrument to observe O17, tune probe (with water sample in the magnet), pulse a few hundred times (no recycle delay and a short aquisition time) with a resonable flip angle. Once you see the signal, measure the w1/2 of the peak and reset the acquisition time to 1/(w1/2). Then calibrate the pulse width (PW90). You generally run O17 spectra with no recycle delay since relaxation is dominated by quadrupole relaxation. The exercise is to pulse as fast as you can. If you want to quantitate a spectrum you may need to varify that your acquisition parameters will allow quantitation just as you would for any other NMR experiment. Incidently, water is the "TMS" for O17. Hope this helps. Regards, Dave Lankin ------------------- Hello, It is very easy to see in water. …. On the other hand, seeing O17 in "real" samples requires a lot of scans. Fortunately, because of the quadrupole, the relaxation is fast. We typically set the d1 times (Bruker or Varian) to 0s because T1 relaxation takes place during the FID. For one sample lately I wrote a Hahn echo sequence, because quite a bit of signal was lost in the dead time of the probe. I do not know anything about the temperature and pH dependence. For any nucleus, my first book to look at is "Handbook of High Resolutions Multinuclear NMR", C. Brevard, P. Granger, Wiley, 1981. Good luck Ulli Ulrike Werner-Zwanziger ------------------------ Yes, we used to run O17 all the time at 54.2 MHz. It is a fairly easy experiment and won't take much machine time. We used O17 linewidths to measure "water mobility" in starch -water mixtures. The line width for pure water was about 48 Hz. Also, Berger, Braun, Kalinowski has a chapter on O17. Gary Juneau. ________________ >Recommend any references? …. A lot of work with 17O was done in Physical Chemistry (e.g. Lennart Piculell - spelling? -) at the University of Lund, at least in the 1980s. _______________ Roger, Look for papers by John Hunt and Harold Dodgen. Then did lots of O17 - metal complex stuff in the 80's. Back then, O17 was the most expensive commodity on the planet, so the concentrations were as low as the fields. Dr. Doug Wheeler University of Wyoming ______________ A good reference book for many 'different' nuclei used to be 'NMR and the Periodic Table' by Harris & Mann. If you can't track a copy down try contacting Brian Mann directly who will I'm sure be happy to help out Ian Marshall Analytics Group , SCYNEXIS Europe Ltd. -------------------- I've used PW90 and AT = 0.1 s (or in some cases shorter), thus obtaining good S/N with D2O in just a few minutes. Probe ringing can be a problem at frequencies lower than ca. 40 MHz. Joan Mason has a good chapter in her book "Multinuclear NMR". David French ------------------------ The reviews by Kintziger (1983) in 'NMR of Newly Accessible Nuclei', P. Laszlo, ed., and Gerothanassis (1994) in Progr. NMR Spectroscopy' are the ones I know, likely to be more out there. Good Luck! Lazaros Kakalis Rutgers University at NewarkReceived on Thu May 02 2002 - 18:37:34 MST
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