I am referring to the application note NM180014E. Need for high resolution 2D spectra. See attached
I have tried the HMBCAD pulse sequence for this I narrowed the spectral width of the carbon to the area of interest. I assume I only should narrow the carbon spectral width and keep the proton width wide to see all the protons.
The pulse sequence on the diagram looks a bit different than the gHMBCAD but shows a selective pulse.
The application note is using REBURP but the gHMBCAD is using WURST. Can I change this or is it necessary? I think the question is how do I change it as it is greayed out.
Adding Ashok, Adolfo and ET as they might have some thoughts or advice regarding band-selective hmbc.
If you look in the experiment library of the std kit you might see 2 y band selective hmbc’s.. y_sel_ct-hmbc_pfg.jxp and y_sel_hmbc_pfg.jxp. I’m assuming they are in Delta 5 kit as I am looking in Delta 6 here – have no old Delta 5 stuff anymore myself. At high resolution the constant time one might be seriously good.
I’ve not played with those myself (had no need) but I know Ashok often does band-selective ghmbc as a part of demos and likely has the experiment in a routine automation script. I am unsure of the experiment he uses but the results are excellent!
No problem swapping the wurst for reburp in existing ghmbcad but I think these other sequence options will work better for narrow bands.
Another thing to keep in mind is the very nice experiment published by Ad, Kathleen, and Greg long ago. Attaching paper. I like the look of that one. We could code it up and compare with the selective hmbc choices in the kit. It would be fun to do some high-sensitivity NMR as right now I’m trapped in F-C adequate world.
There is a y_sel_hmbc_pfg since at least Delta 5.3.1. The CT version appeared in Delta 6.
I use the attached version (Delta 5), which is the same as the default but you do not need to define anything in the pulse section. I.e., in the default version you have to figure out a length for the shaped pulse that will refocus the bandwidth of interest. In my version that pulse length is automatically calculated as 1.1 times y_sweep (you can adjust it to any other number you prefer), so you only need to set y_offset and y_sweep to the bandwidth of interest. This also means you can use this experiment in the automation script as a new method copied from the HMBC, where you just change the name and the collect statement to use this other pulse sequence.
Though I tend to favour simply running the standard HMBC with NUS, and folding if needed ( you can easily simulate folding in Delta), over running a band selective version, but this is just a matter of preference.
For very long range couplings what you want to use is the LR-HSQMBC with the constant set to 2 Hz or similar, as very low coupling constants means to setup the standard HMBC very long delays, and too much magnetization is thus relaxed throughout the experiment, while the LR-HSQMBC will use shorter delays. You don’t want to run only the LR-HSQMBC as its response is quite different from the standard HMBC.