gHMQC

 

Set up appropriate 1H parameters. Normally should acquire 1D 1H spectrum first.

 

pw = 1H pulse, should be 90º pulse

 

tpwr = high power for 1H; should be set according to pw, or is correlated to pw.

 

nt = number of scans, should be multiple of 2, but 1 is acceptable

 

ni = number of t1 increments, points in t1 dimension, at least 64, 128 is preferable

 

np = number of points in t2 dimension, must be even number, 2048 is standard

 

d1 = relaxation delay; normally should be slightly longer than in gCOSY, so 1.5 seconds is normal, but aromatic (or vinyl or methyl) protons usually need 2.0-2.5 seconds for optimal signal-to-noise

 

 

Steps:

 

1) Acquire 1 scan of 1H 1D experiment. Set cursors ~0.5 ppm beyond last proton resonance on both sides of spectrum, type command:

movesw

 

2) Re-acquire 1H 1D experiment (this is only required for 1H 1D on side of 2D spectrum)

 

3) Move parameters to another experiment. To move parameters from experiment 1 to experiment 3 type command:

mp(1,3)

 

4) Change to experiment 3, type command:

jexp3

 

5) Set gHMQC parameters with setup macro, type command:

 

6) Spin will likely turn off, if it does not, open Acqi window and manually turn it off. Lock Level should not drop more than ~5 %-10 %. If it does, you should reshim non-spin shims- X1, Y1, XZ, and YZ, and on higher field (500/600) X2Y2 and XY

 

7) Set the number of scans (nt) to appropriate value, generally 1 or 2 (it is preferable for nt to be a multiple of 2; nt might need to be increased for sufficient signal-to-noise, generally nt = 2 is sufficient if decent 1H spectrum can be acquired in 32 scans), type:

nt=2

 

8) Set the number of points in t1 dimension (second dimension) (ni), generally 128-256 are suggested, 128 is normally sufficient, type:

ni=128

 

9) Set d1 time, normally should be slightly longer than in gCOSY, so 1.5 seconds is normal, but aromatic (or vinyl ) protons especially in non-viscous solvent usually need 2.0-2.5 seconds for optimal signal-to-noise

 

10) Set the parameters sw1, dof, and j1xh; sw1 = spectral width in 13C dimension, the default is ~-10 to 160 ppm; if you have a protonated 13C beyond that range then sw1 must be increased or dof (the center of the carbon spectrum must be changed); the default value of j1xh (the 1-bond 1H/13C coupling constant) is 140 Hz, which is approximately correct for aliphatic proton/carbon pairs, aromatic 1-bond 1H/13C coupling constants are 170-250 Hz, so j1xh = 180

 

11) Start acquisition, type command:

go

 

12) Process data with VNMR: processhsqc

13) If spectrum has yellow streaks and purple streaks horizontally across the spectrum, then the spectrum should be phased; set cursor on peak, type:

ds

then manually phase, be careful to only click once on spectrum during phasing, only rp (or rp1 phase correct should be changed)

redraw 2D type:

dpn10

If spectrum still has streaks in horizontal direction more phasing is required including lp (or lp1) phase correct. If spectrum has yellow/purple streaks in vertical direction, then the other dimension needs to be phased, so switch the axes, type:

trace = 'f1' (or 'f2', depending upon which axis is currently the x-axis, then type:

dpn10

 

14) Spectrum should be appropriately referenced already, but you should confirm this; if necessary re-reference by putting cursor on appropriate diagonal peak and type (assuming CDCl3):

rl(7.26p)

rl1(77d)

dpn10

 

15) Adjust vertical scale with vs +20% and vs -20% menu buttons or with middle mouse button or manually changing the parameter, vs2d, so vs2d = 100 (the lower the number, the less noise displayed), then redraw 2D with dpn10 command

 

16) Print with full rectangle, type:

full

dpn10

pn10

for only positive peaks:

p10

for only negative peaks:

n10

 

17) Save data, type:

svf('filename')