Record a normal ¹H NMR spectrum of the sample and optimize the spectral width. For the 2D experiment you have to set:

td2: 1 k data points in F2 td: 256 data points in F, sw2: 10 ppm swl: 10 ppm o1: middle of ¹H NMR spectrum p1, p2: 90° ¹H transmitter pulse dl:2s initial value for ¢, evolution: 3 μs increment for ¢, evolution: I/sw1 g1, g2: sinusoidal-shaped field gradients with 1% truncation, 2 ms duration and 0.1 T/m strength, with gradient loop counters, ring-down delays (100 ps), lock blanking and gradient coil blanking switches according to actual instrumentation used. Gradient strength ratio | : 1. ds: 4

5. Processing

Apply zero-filling in F, to 512 words in order to have a symmetrical matrix of 512x512 real data points. Use unshifted sinusoidal windows in both dimensions. Apply complex Fourier transformation as for the standard N- or P-type COSY. Instead of phase correction use the absolute value mode; symmetrization of the matrix may be performed.

6. Result

The figure shows the expansion of a 2D spectrum obtained on an AMX-500 spectrometer with an inverse multinuclear z-gradient probe-head and a BGU (10 A) gradi- ent unit. Symmetrization has been used. Note that the intensities of the cross-peaks reflect to some extent the magnitudes of the spin coupling constants.

7. Comments

Gradient experiments are best understood by using shift operators /’ and [ and constructing a coherence pathway diagram like the one shown above. The first pulse of the COSY sequence creates –/, magnetization, which can be written in shift operator terms as in Equation (1).

-ly=-tiit -") (1) Both coherence levels, the /’ and J paths are, after ¢, evolution, dephased by the first gradient g!. The second 90° pulse transforms /’ and J according to Equation (2).