Valentin Ananikov
AVANCE HomoSpoil Mini-FAQ
"The first step of trouble shooting is trouble finding" (Murphy's Law No57, revision)
Below one can find answers to some Frequently Asked Questions we have encountered with. Note, all the hardware-related things have been checked on AVANCE DRX500 spectrometer and might be different on the other systems.
Contents
Q1) Hmm.., it seems, it doesn't work. What should I check first?
Q2) Nothing is working...
Q3) HomoSpoil Pulse does not exist.
Q4) WATERGATE: water signal is oversuppressed.
Q5) WATERGATE: lineshape and intensity distortions.
Q6) COSYDQF goes wrong.
Q7) What NOESY sequence is better?
Q1) Hmm.., it seems, it doesn't work. What should I check first?
A1) Z1-shimm range. It should be 3, in this case the range of Z1-shimm is -+100000. Z1-range parameter is accessible via BSMS keyboard.
Q2) Nothing is working...
A2) First of all, check the hardware. Download and execute the following pulse program:
-rw-r--r-- 1 valentin user plain text file tesths.val
The program consists of the single HomoSpoil pulse without acquisition, so no FID should appear. During the execution of the program one must see the same influence to the lock signal as with the normal gradient pulse: the lock signal falls down and restores after the some time. If it doesn't- it is a problem: HomoSpoil Pulse does not exist. Unless you are expert, stop any experiments and wait for the serviceman ;-).
Q3) HomoSpoil Pulse does not exist.
A3) The only thing you could check is the cable connection. Open the doors of the AVANCE cabinet and look to the SCB13R panel: the cable marked "HOMOSPOIL" must be connected into the "HomoSpoil Start Pulse" pin.
Note: If you have just connected the cable, HomoSpoil Pulse normally should not appear. Reboot The Hardware!!
Explanation: All the elements and connections of the hardware are detecting during the "POWER ON" tests.
Q4) WATERGATE: water signal is oversuppressed.
A4) That is usual case and it is the problem of the WATERGATE itself. Adjust "O1", "P0", and HomoSpoil pulse amplitude.
Q5) WATERGATE: lineshape and intensity distortions.
A5) This is the most complicated problem.
i) If there are only intensity distortions very likely "PL18" and/or "d19" parameters should be optimized.
ii) If the lineshape distortions are not tragical, just set "lb=0.3-1", EM,FT,..., and forget about this.
iii) If all the singlets are looking as doublets, try to reoptimize d16 and compensation parameters.
Q6) COSYDQF goes wrong.
A6) If COSYDQF experiment has been stopped with the "stop" command or aborted due to error it might start from the wrong pulse, the second defined pulse might be the first one actually executed. Make 'reset sequence' before the next attempt. The same is true for any experiment utilizing more than one HomoSpoil pulse.
Advice: Never abort HomoSpoil experiments with the "stop" command.
Q7) What NOESY sequence is better?
A7) Both methods usually give the same results, therefore choose the most convenient one. In principle, the sequence with one gradient during the entire mixing time might produce more clean spectra, since it is not effected by the diffusion processes. Of course this is not always 100% correct.
(c) Ananikov VP 1998
Valentin P. Ananikov
NMR Lab
N.D. Zelinsky Institute of Organic Chemistry
http://nmr.ioc.ac.ru/Staff/AnanikovVP/