4. Acquisition

Time requirement: 20 min

Sample: 3% strychnine in CDCl₃.

Record normal ¹H and ¹³C NMR spectra of the sample and optimize the spectral widths for CH_n signals. Change to the 2D mode of the spectrometer and load the phase-sensitive HSQC pulse program with echo/anti-echo acquisition and shaped 180° pulses. Inform yourself about the usage and power requirements of the adiabatic pulses on your instrument. You have to set:

td2	2 k data points in F₂
td1	256 data points in F₁
sw2	10 ppm
sw1	150 ppm
offset of ¹H frequency	middle of ¹H NMR spectrum [4.5 ppm]
offset of ¹³C frequency	middle of ¹³C NMR spectrum [70 ppm]
p1, p4, p6	90° ¹H transmitter pulse [9.75 μs, −2.8 dB]
p2, p5, p7	180° ¹H transmitter pulse [19.5 μs, −2.8 dB]
p3	2 ms ¹H trim pulse
p9, p11	90° ¹³C decoupler pulse [20 μs, −3.3 dB]
p10	180° ¹³C decoupler pulse [40 μs, −3.3 dB]
p8, p12	adiabatic 180° ¹³C decoupler pulse [on Bruker instruments: crp 60, 0.5, 20.1; 500 μs, −1.2 dB]
d1	2 s
d2	1/[4J(C,H)] = 1.72 ms, calculated from ¹J(C,H) ≈ 145 Hz
d3	effective gradient length g1 = 1.05 ms
initial value for t₁ evolution	3 μs
increment for t₁ evolution	1/[2·sw1]
¹³C decoupler attenuation and 90° pulse for GARP	7.5 dB, 70 μs
g1, g2	sinusoidal-shaped field gradients, 1 ms duration and ca. 0.1 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: 80 : 20.1; g1 switched to negative according to echo/anti-echo scheme
ds	2
ns	2

5. Processing

Apply zero-filling in F₁ to 512 words in order to have a matrix of 1024 × 512 real data points. Use an exponential window in F₂ with lb = 2 Hz and a π/2-shifted squared sine bell window in F₁. Choose the echo/anti-echo FT mode of the software corresponding to the acquisition technique. Phase correction is necessary in both dimensions.