>-----------------
>Letitia J. Yao
>Department of Chemistry
>University of Minnesota
>e-mail: yaoxx006@maroon.tc.umn.edu
>*******************************************************************************************
Letitia,
I have used a simple addition to pulse field gradient HMBC and HMQC type pulse programs (called presat,
shown below) for presaturation of two single quantum peaks in a polymer. The two peaks that I supress
are the repeating CH2's and CH3's in polyisobutylene (-CH2-C(CH3)-) that are 100-500x larger than the
peaks that I am interested in. I have added the following presaturation loop, using the mule program
to create two amplitude phase modulated selective pulses, to the beginning of gradient enhanced
inverse experiments. I typically use a 1D analogue to tweak the presaturation pulses. This allows me
to play with both the selective pulse width and pulse power to obtain the best supression with the least
amount of disturbance to the surrounding peaks. The 1D sequence is given below as presat_tweak.kfw.
;presat_tweak.kfw
1 ze
2 d12 tlo
3 p28:tp1 ph29
4 d13
5 lo to 3 times l4
6 d12 thi
7 p1 ph1
8 go=2 ph31
9 d11 wr #0
10 exit
ph29=0
ph1=0 2 2 0 1 3 3 1
ph31=0 2 2 0 1 3 3 1
The presaturation loop that I use at the beginning of 2d inverse experiments is given
below as presat.
;presat
1 ze
2 d11 tlo do
3 p28:tp1 ph29
d13
lo to 3 times l4
d12 thi
Some typical parameters I use on my AMX500 are a 512 points gaussian pulse (TPNAME1) using a
38 ms soft pulse at a transmitter frequency of 5ppm. The peaks that a supress are at 1.4 and 1.1 ppm.
A typical power setting (tp1) for the soft pulse is 54 db using tlo. Again, you should tweak these prameters using a
pulse sequence like presat. I have had very good success at completely nulling the two SQ peaks in the
1D spectrum. However, they are not nulled nearly as well in the 2D spectrum, probably due to T1
relaxation duing the evolution and delay times of the 2D sequence. I should add that my spectrometer
configuration is an E-coupler for the proton channel and a bltx300 for the x channel. If you have any
questions feel free to call or e-mail.
Best Regards,
Kurt
------------------------------------------------
Kurt Wollenberg
The Lubrizol Corp.
29400 Lakeland Blvd.
Wickliffe, OH 44092
e-mail: kfw@lubrizol.com
phone:216-943-1200 x2026
fax:216-943-9022