Sample Preparation and Time Required - 1D NMR
A. Sample Preparation.
We use 5 mm tubes, Kontes grade 897130 (N51 glass) or better, available from Fisher Scientific. For variable temperature work, use 897230 (Pyrex glass) or better. Do NOT use disposable or "benchtop" grade tubes in ANY NMR since they are often irregular and could result in damage to the instrument. All samples must be dissolved in deuterated solvents in order for the field-frequency lock to function. 600 ul is the normal volume. Sigma -Aldrich is a supplier of deuterated solvents.
B. How much sample and acquisition time is required?
Proton - only 1-5 mg of a small molecule is necessary for 5 min spectrum. Smaller amounts require longer scan times.
Carbon, direct observe- the table below is a guide for a small molecule (MW=334) on the 400SL. The detection limit can be lowered with the use of Shigemi tubes. See the Carbon training handout for more details. Please note: 2D HSQC is at least 15 times more sensitive than 1D carbon direct observe.
- Sample Quantity
- 25 mg
- Molarity (mM)
- 75
- Approximate Time Required for 13C direct observe
- 5 min
- Sample Quantity
- 7.5 mg
- Molarity (mM)
- 22.5
- Approximate Time Required for 13C direct observe
- 30 min
- Sample Quantity
- 3 mg
- Molarity (mM)
- 9
- Approximate Time Required for 13C direct observe
- 180 min
- Sample Quantity
- 1.5 mg
- Molarity (mM)
- 4.5
- Approximate Time Required for 13C direct observe
- 12 hours