Table 5 Standard operational procedure for dDNP experiments.
From: Performance and reproducibility of 13C and 15N hyperpolarization using a cryogen-free DNP polarizer
No | Operation | Duration | Comments | Norm values |
|---|---|---|---|---|
1 | Check T of VTI (P1, P2) | T = 1.38–1.4 K P1 ≈ 1.3 mBar P2 ≈ 250–350 mBar | ||
2 | Warm up stock CA-radical concentrate until liquid | 10 min | Protect from light | |
3 | Flush fluid path with air | 10 min | Automatic | |
4 | Add CA-radical concentrate to cup | 5 min | Use micropipet, add to the bottom, avoid smudging to walls | 18–19 µL ≈ 22 mg (for 13C) And 50 uL ≈ 50 mg (for 15N) |
5 | Prepare liquid nitrogen (lN2) | 2 min | Place non-magnetic dewar next to the magnet | < 500 mL of lN2 |
6 | Connect sample cup to polarizer: - Connect empty cup - Flush with He - Disconnect cup, connect cup with a sample - Dip cup in lN2 - Pressurize fluid path | 3 min | Mark vial to avoid damage to thread by over tightening Use cryogenic gloves Immerse slowly into lN2 Pressurize while in lN2 | Immersion into lN2 for 30 s |
20 s | ||||
7 | Insert cup into VTI | 5 min | Hurry but stay calm: open airlock, remove plug, insert sample, close airlock, start automatic insertion procedure Manually guide tube if needed. Use gloves | |
8 | Position cup in VTI/NMR coil | Mark lowest position on tube e.g. with tape | 10 mm above lowest position | |
9 | Check that the NMR coil is in resonance | 2 min | Adjust tuning and matching capacitors | Tune within ± 20 kHz, match 1–2% |
10 | Wait for temperature T and pressure to stabilize (P1, P2) | 5 min | Insertion causes temperature and pressure increase | Close to starting temperature, e.g. T = 1.38 – 1–4 K |
11 | Start DNP 11a: start monitoring 13C NMR (SpinIt) 11b: start DNP (SpinAligner) | 60 min | Check that µW is on Check 13C NMR signal | |
12 | Prepare MRI/NMR | Adjust resonance of the probe, create a new protocol, shims of the system, create new project, free space to ease transport | ||
13 | Inject dissolution medium in heater | Standard dissolution medium suitable for tracer | 5 mL | |
14 | Initiate heating of dissolution medium | 5 min | Close the cover of polarizer | Automatic, ready when 11 bar reached |
15 | Prepare receiver vessel/syringe | Weigh and label NMR tubes and place receiver in the stray field | ||
16 | Put on safety equipment: Goggles, gloves | Caution! Hot liquids, high pressures! | ||
17 | Raise cup | 30 s | Raise cup above lHe level to reduce lHe boil off | Rise by 8 cm |
18 | Execute dissolution | < 30 s | Hot liquid at high pressure and speed will be ejected | Automatic |
19 | Collect hyperpolarized medium e.g. to syringe and apply | 5 s | Draw in syringe for manual injection, transfer via tubes to detection site | |
20 | Transfer NMR samples or syringe to NMR/MRI and execute pulse sequences when sample is at the detection position | 30 s | A fast transfer is necessary | |
21 | Take out the sample cup, conserve the airlock, perform the cleaning | 15 min | Wash the heater 3 times with deionized water, then dry at least 10 min | 10 mL of water to clean the system each time |
