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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? Thanks!! |
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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. |
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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. Hmm, in most 2D experiments calibration of pulses is very important for the correctness of the experiment itself. What follows from your statement is incorrect. - Evgeny Fadeev (Jun 28 '12 at 21:02) I depends a little on the experiment. Some (e.g. COSY) are more forgiving of pulse mis-calibration than others. - Kirk Marat (Jun 29 '12 at 07:21) |
