So it is pretty much always recommended to calibrate the 90 for 1H for any 2D experiment... Cosy, Noesy, HSQC, etc...
But when I have calibrated them, there is relatively little change... say from 7.32 to 7.65... Of course for all I know that could be a significant change...
Anyway, how 'off' does the 90 need to be to make a noticeable difference? If you have a concentrated sample, is it less sensitive to the 90?
asked Jun 28 '12 at 12:43
IMHO it always depends on particular 2D sequence. Some of them are quite tolerant to miscalibrations, some - not. Since 90 deg. pulse miscalibration makes our spin vector behaviour a little bit different, tolerance of pulse sequence depends on it's complexity. E.g. ordinary gradient COSY (of 2 pulses) would be quite tolerant, but phase-cycled HSQC with BIRD suppression of 12C (of 10 proton and 6 carbon pulses) must be quite sensitive.
P.S. I always check proton 90 pulse before 2D (it takes just 2 minutes), so recommend to you.
answered Jun 29 '12 at 09:04
the 90 pulse calibration is necessary for the spectra where you need to get maximam intensity but in the case of 2D the intensity is doesn´t important.
answered Jun 28 '12 at 13:00