Thank you for the kind replies. In short, for LR COSY tau delays ranging
from 30 to 500 ms were suggested.
-------------------
According to my ref, a typical tau sandwiching the P2 pulse is 200 ms
-------------------
A pretty typical tau is 50ms, and can get as long as 500ms. You will
observe sub-1Hz J's using 50ms.
-------------------
you will get maximum signal intensity for a cross peak when the delay is
1/2J. So starting at 30 msec will give you both short and long range
couplings, with longer delays you will enhance the long range ones.
-------------------
It's a balance between S/N and how small a J you want to detect. If
something like a benzylic coupling then 50-100ms should be fine. If groping
for something very small, the try up to 300m.
-------------------
...
Simple COSY works best for coupling constants of ca. 4 to 15Hz. Thus, for
smaller couplings, the delays between the two pulses should be relatively
long.
I usually use between 150 and 200ms (each), depending on the size of the
molecule, and the results are good.
Because of these two additionally long delays, I usually record a long range
COSY with 2 times more scans than a simple one.
-------------------
200 ms.
Check page 377 of the book 200 and more NMR.
-------------------
-----Original Message-----
> From: ELDRED, DONALD V. (DVELDRED)
> Sent: Friday, May 06, 2005 1:30 PM
> To: ammrl_at_ammrl.org
> Subject: Long Range COSY
I have loaned out my reference book for Long Range COSY experiments. Could
someone refresh my memory as to where a good starting place is for the tau
delay between P1 and P2.
Thanks,
Don Eldred
Associate Analytical Specialist
Dow Corning Corporation
2200 W. Salzburg Rd.
Auburn, MI 48611
Phone: (989) 496-6843
Fax: (989) 496-5121
Received on Wed May 25 2005 - 23:34:42 MST