The 400 MHz systems can operate
with three multi-nuclear probes, and the 400 MHz Ascend system has a sample
exchange unit, Little sampleXpress for 16 samples:
5mm BBO probe
broadband probe for direct
that enables the analysis of nuclei as
, 19F, 31P, 15N, 17O,
b) a 5mm BB
c) a 5mm DUL probe
that enables the analysis of the nuclei
600 MHz system can operate with two probes and has a sample exchange
for 60 samples:
a 5mm TXI probe with triple resonance,
13C - 15N
b) a 5mm BBO Prodigy cryogenic probe, cooled with
liquid nitrogen, with a BCU temperature control unit, enabling to
operate in the range of temperatures:
0ºC - 80°C .
All the pobes have automatic
tunning / matching (atma) and Z field gradients.
most common NMR analysis are 1D and 2D experiments in
which the signals of the possible nuclei are analysed, depending of
the used probe, and in the case of 2D experiments, it is also possible to
look for the correlations between the nuclei
1H - 1H, 1H
- 13C or 1H -
Sample requirements and
for analysis must be delivered in the liquid phase, with adequate
identification. The samples must be delivered in appropriate tubes (quartz),
compatible with the frequency of the equipment (400 or 600 MHz) and with a
diameter of 5 mm. The solutions should be prepared in deuterated
solvents and must be completely soluble in the selected solvent. The ideal
amount of sample is 5 - 10 mg for
and above 20 mg for
However, it will depend on sensitivity, the isotopic abundance, the nuclei
to analyse, the instrument sensitivity, the spectrometer frequency, and the
kind of analysis required.
Specific information can be obtained in several websites dedicated to NMR
experiments or in direct contact with the laboratory.
Since the sensitivity is one of
the more important factors in any NMR experiment, attention must be paid to
the sample volume. The minimum sample volume required is 600
ml, for a
tube length of 140 mm. The resistance of the tube must be checked, always,
before sample preparation, since it can break inside the instrument during
analysis causing serious equipment damage.
experiments are usually performed overnight or during the weekend.
The Nuclear Magnetic Resonance Laboratory at UP is part of the
Portuguse NMR Network: