I seem to be having some problems with my parameter sets for our HMQC and
HMBC experiments. I am running the experiments on an AMX-600 with a X-32
and Aspect3001 computer system.
First the samples are dilute 3-4 mg(MW = 600 to 1000 gm/mole). Can I run a
HMBC and HMQC (inverse detection) on a sample this dilute.
Yes, if you are brave and have about 24 hours of machine time, more or
less depending on whether you are running 13C or 15N by inverse detection.
If you need to ask, it can be assumed you have natural abundance samples.
If I can, what
parameters do I need to check or calibrate before I rum the experiment.
The most important is to center the transmitter frequency on the
appropriate region of interest. To save time you should set this up with an
enriched sample. For 13C you should see aliphatics at around 10 ppm through
to aromatics at around 140 ppm, via inverse detection, so you should set the
transmitter frequency accordingly. For 15N you are likely only interested in
the amides, but you may see others depending on the solvent. This region
extends from around 100 to 126 ppm. You might wish to set up the transmitter
frequency for this using 15N enriched urea which is at 75 ppm, but use
caution because of the negative gyromagnetic ration of 15N.
I have checked the 90's in the decoupler and transmitter channel. Do I need
to do this for every sample or just every so often as part of my regular
calibration and shimming work.
I don't think you need to do this each time.