4. Acquisition

Time requirement: 5 h

Sample: 0.5 ml salicylaldehyde with 0.2 ml [D₆]DMSO.

Record normal ¹H and ¹³C NMR spectra of the sample, note the required spectral widths and note the offset of the middle of each spectrum. Change to the 2D mode of the spectrometer and load the required pulse program. You have to set:

td2: 1 k data points in F₂
td1: 128 data points in F₁
sw2: 10 ppm (for short acquisition time due to GARP decoupling)
sw1: 180 ppm (C,C double-quantum frequency, enter in Hz)
o1: center of ¹H NMR spectrum [8.9 ppm]
o2: center of ¹³C NMR spectrum [157 ppm]
p1, p4, p6, p8, p10: 90° ¹H transmitter pulse [8 μs, 5 dB]
p2, p5, p7, p9, p11: 180° ¹H transmitter pulse [16 μs, 5 dB]
p13, p15, p19, p21: 90° ¹³C decoupler pulse [13.5 μs, 0 dB]
p12, p14, p16, p18, p20, p22: 180° ¹³C decoupler pulse [27 μs, 0 dB]
p17: 60° ¹³C decoupler pulse [9.0 μs, 0 dB]
p3: 2 ms ¹H spin-lock purging pulse
d1: 2 s
d2: 1/[4J(C,H)] = 1.56 ms, calculated from ¹J(C,H) ≈ 160 Hz
d3: 1/[4J(C,C)] = 31 ms, calculated from ²/³J(C,C) ≈ 8 Hz
d4: 1.05 ms = effective gradient duration
d5: d3 minus effective gradient duration
d6: 1/[4J(C,H)] = 1.56 ms (CH moieties only)
initial value for t₁ evolution: 3 μs
increment for t₁ evolution: 1/[2·sw1]
g1, g2, g3: sinusoidal-shaped field gradients, 1 ms duration and ca. 0.2 T/m strength, with gradient loop counters, ring-down delays (50 μs), lock blanking and gradient coil blanking switches according to actual instrumentation used. Gradient strength ratio: −78.4 : −77.4 : −59 (exact γ-ratios), sign of g3 varied according to echo/anti-echo mode.
Decoupler attenuation and 90° pulse for GARP [70 μs, 14 dB]
ns: 128
ds: 32

5. Processing

Apply zero-filling to 1 k real data points in F₁ to obtain a matrix of 512 × 1k real data points. Use an exponential window in F₂ with lb = 7 Hz and a π/3-shifted squared sinusoidal window in F₁. Choose the echo/anti-echo FT mode of the software corre-