4. Acquisition

Time requirement: 10 h

Sample: D₂O with 10% Methanol, 5% n-Butanol and 5% Triethylene-glycol.

Set and control the temperature to 300 K. Use a high air-flow to avoid convections in the sample. First record a minimal ¹H NMR DOSY spectrum (ns = 1) with a gradient ramp of 8 gradient strengths in order to observe complete signal decay for a given diffusion delay and gradient power. Set the second channel of the spectrometer to ¹³C and load the DOSY-HMQC pulse program. You have to set:

td3: 1k data points in F₃
td2: 64 data points in F₂ (gradient ramp)
td1: 64 data points in F₁
sw3: 6 ppm
sw1: 80 ppm
o1: middle of selected ¹H NMR region [3 ppm]
o2: middle of selected ¹³C NMR region [46 ppm]
p1, p3, p4: 90° ¹H transmitter pulse
p2, p5, p6: 180° ¹H transmitter pulse
p7, p8: 90° ¹³C decoupler pulse
d1: 2 s
d2: diffusion delay 75 ms − 3 times effective gradient duration
d3: 1/[2·J(C,H)] = 3.5 ms
d4: 1/[2·J(C,H)] = 3.5 ms − effective gradient duration
g1, g2, g4, g5 sinusoidal-shaped bipolar field gradients (gradient strength ratio: −1 : 1 : −1), 1.8 ms duration; ring-down delays [50 μs], lock blanking and gradient coil blanking switches according to actual instrumentation used. For the variable gradients used during this experiment you have to define a linear gradient ramp containing 64 values ranging between 2 and 95% of the total gradient strength provided by the gradient amplifier; details are very dependent on the software used. g3 is a spoil gradient with the strength 17 of 1 ms duration, g6, g7 and g8 are the gradient pulses for HMQC in the ratio 50 : 30 : 40.1.
¹³C decoupler pulse for GARP decoupling [75 μs, 11 dB]
ds: 8
ns: 4

5. Processing

Apply zero-filling in F₁ to obtain a 512 × 128 × 128 data matrix. Use a sinusoidal window in the F₃ and a squared π/2-shifted sinusoidal window in F₁. Transform only in F₃ and F₁ directions, and apply a base-line correction in both these dimensions. In the 3D cuboid, each signal will now display a decay curve in F₂ as the gradient strength increases. The extraction of decay constants and their transformation into a