Length of NMR tubes for the automated system

The length of the NMR tube must be at least 17 cm below the lids or the Parafilm. This length must also be maintained before the attachments of screw caps, ground joints of Young Tubes start to begin.

If the automated system’s gripper catches on the lid or the unevenness of the attachment or the Parafilm, the tube cannot be transported correctly. It may hang crookedly in the gripper and therefore not be placed correctly. In the worst case, the glass of the tube may break within the NMR spectrometer. This would result in a repair by the manufacturer (duration at least 6 months).

Preparation of the samples

Amount of substance:

• For ¹H measurements: 5–20 mg (natural abundance: 99.9%)
  A higher amount of substance leads to broader signals and poorer resolution 
• For ¹³C measurements: 5 mg per ¹³C atom (natural abundance: 1.1%)
  Smaller amounts of substances lead to longer measurement times. (half the amount of substance = four times the measurement time, etc.) 

Filling the NMR tubes

• Stinking samples should be wrapped in parafilm or filled into ground joint glass tubes. 
• Deuterated solvents (anhydrous) or D₂O capillaries should be used. (D₂O capillaries not for the Fourier 300) The deuterium signal is used in the NMR spectrometer to counteract the drift of the magnetic field and ensure the homogeneity of the magnetic field. (so called lock) Measurements without a lock lead to poorer results. 
• The solution should be free of suspended matter and magnetic and paramagnetic impurities. 
• Filling level: 4–6 cm; the spectrometers are shimmed to this filling level. (shimming = Homogenizing the magnetic field) 
• The information sheet „Length of the NMR tubes” must be observed. 
• Only undamaged and clean tubes will be accepted.

NMR Order Form

Mandatory fields: Name, date, sample name, solvent, assistant (if applicable), working group, experiments → tick or possibly enter further experiments in the comments field (reverse side can also be used)

Naming

• Samples from the "OC-Anfängerpraktikum" begin with OCA name abbreviation-…
• Samples from the „Synthesepraktikum” begin with ISP-OC-name abbreviation -… or ISP-AC-name abbreviation …
• Samples from the „Forschungspraktika” begin with OCF-name abbreviation-… or ACF-name abbreviation-…
• Samples from the „NMR-Praktikum” begin with NMR-PR-name abbreviation-…
• Bachelor’s degree (recommendation): BA-name abbreviation-…
• Master’s (recommendation): MA-name abbreviation-…
• Other: name abbreviation-…

Measurement range:
If a different measurement range is required, this is entered accordingly under ‘sw’ and ‘o1p’.

• sw = Measurement Range of the spectrum in ppm
• o1p = Centre of the spectrum in ppm

Notes on cleanliness

• The NMR tubes have to be tightly closed and clean (cleaned on the outside with isopropanol).
• This also applies to the vessels in which they are stored. The cotton wool inside and the order forms have to be clean, too. Of course, the sample vessels have also to be free of damage.
• Unclean or damaged glass vessels will be retained by us!
• Inobservance will lead to gradual contamination of the probes and the spinners. The consequences are: poor shim, sticky tubes in the probe, sending the probe to the manufacturer for cleaning → duration at least 3 months.