Absolute-Value COSY Experiment

Data Collection

1. Set the VT unit to regulate temperature. See Temperature Regulation.

2. Obtain a 1H 1D spectrum with an optimized spectral window (sw). Uninteresting peaks may be folded. Save the FID.

3. Type cosy to change the parameters to the absolute-value COSY experiment.

4. Change the following parameters:

pw set to 90 pulse width listed at spectrometer

p1 set to 90 pulse width listed at spectrometer

d1 set to 3T1 - at. 2 seconds is a typical value.

d2 0

nt multiple of 4

ss 2

sw sweep width in acquisition dimension

sw1 sweep width in first (t1) dimension. Set sw1=sw

td 1024. Can be set to 2048 if fine digital resolution is absolutely necessary.

digital resolution in acquisition dimension = sw/td

ni multiple of 32, maximum of 1024, values of 128, 256, or 512 are recommended.

digital resolution in first (t1) dimension = sw1/ni

5. Type time to determine experiment time. Adjust d1, nt, and ni to use the remainder of your scheduled time. Follow spectrometer ettiquete and plan to spend the last 5 minutes of your scheduled time to prepare the spectrometer for the next user.

6. Turn off the spinner. If the lock is lost, increase lock power.

7. Type au to start acquisition.

8. When the experiment is finished, save the experiment data.

Data processing

1. Load the experiment data

2. click on main menu, process set parameters, pseudo, large

3. Type fn=2*td fn1=fn

4. Type fpmult1=0.5 pmode='' intmode='partial'

5. Type do2d. The 2 dimensional fourier transformation takes 5 to 10 minutes.

6. Type nm2d to automatically adjust the scaling of the 2D spectrum. To manually adjust the scaling:

A. Position the mouse pointer over a peak and click the left mouse button to adjust the vertical scale so that the peak is no longer visible.

B. Position the mouse pointer at the position of a peak that is not visible and click the left mouse button to adjust the vertical scale so that the peak is visible.

C. Position the mouse pointer within the threshold vertical bar (to the right of the spectrum) and click the middle mouse button.

D. Type vs=new# or type th=new# to change the scaling factors. Type dconi or click on redraw, or main menu, display, contour to update the display.

6. Position the cursor over a diagonal peak and type rl(referencep) where ref# is the ppm value of this peak (i.e., if the cursor is positioned over the chloroform diagonal peak, type rl(7.26p).

7. proj trace

8. line list of islands, or mark

9. Type foldt to symmeterize the spectrum. Symmeterization removes noise artifacts. WARNING: symmeterization may create artifacts that appear to be cross peaks. Analysis of symmeterized spectra should be verified using unsymmeterized spectra.

10. Type acosy to perform automatic analysis of cross peaks that are visible in the graphics window.

11. plotting