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TOCSY
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 8, but 4
is acceptable
ni = number of t1 increments, points in t1 dimension,
must be even number, preferably at least 128, 256 is preferable
np = number of points in t2 dimension, must be even
number, 2048 is standard
slpw (slpwT on VNMRJ 4.2) = spin lock pulse width, must be a 90º pulse with
a pulse width of ~30-35 ms
slpwr (slpwrT on VNMRJ 4.2) = power of spin lock pulse, cannot be more than
49 units, preferably ~43 units, must correlate to slpw
mixT = mixing time; the larger the mixing time the more
transfers will occur (the more protons that will be correlated); generally
80-100 ms (so mixT = .08 or mixT = .1 is sufficient for ~5-8 transfers, 20
ms (mixT = .02) is about right for ~1 strong transfer, one medium and one
weak)
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 TOCSY parameters with setup macro, type
command:
TOCSY
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 4 or 8 (it is preferable for nt to be a multiple of 8; nt might
need to be increased for sufficient signal-to-noise, generally nt = 4 is
sufficient if decent 1H spectrum
can be acquired in 128 scans), type:
nt=4
8) Set the number of points in t1 dimension (second
dimension) (ni), generally 200-400 are suggested, type:
ni=256
9) Set d1 time, 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
10) Set the mixing time (parameter = mixT ); the larger
the mixing time the more transfers will occur (the more protons that will
be correlated); generally 80-100 ms (so mixT = .08 or mixT = .1 ) is
sufficient for ~5-8 transfers, 20 ms (mixT = .02) is about right for ~1 strong
transfer, one medium and one weak)
11) Start acquisition, type command:
go
12) To process data with VNMR tyep: processtocsy
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(7.26p)
dp10
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 dp10 command
16) or Print with full rectangle, type:
full
dp10
pcon(10,1.2) page
17) Save data, type:
svf('filename')
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