Laboratory for Structural Elucidation  - LAE

 

 

Laboratory for Nuclear Magnetic Resonance Spectrometry    

 

Contacts Lic Mariana Andrade, email:  lrmn@cemup.up.pt

                   Scientific Supervisor:   Prof. Maria Conceição Rangel, email: mcrangel@fc.up.pt

          

Laboratory access and services rules:  Rules for Access and Services (pdf)  

                                                                     Access, Services and Training

 

Equipment

Two Digital Nuclear Magnetic Resonance Spectrometers  BRUKER AVANCE III 400 MHz, 9.4 Tesla .

One Digital Nuclear Magnetic Resonance Spectrometer BRUKER AVANCE III HD 600 MHz, 14.1 Tesla .

 

The first Spectrometer was installed in 2008, a 400 MHz Ultrashield Spectrometer, and in 2012 the two remaining Spectrometers were installed, a 400 MHz and a 600 MHz Ascend Spectrometers, versions with updated magnets.

 

The three spectrometers are designed for the analysis of samples in the liquid phase and are equipped with variable temperature units, that depending of the used probe, allow the operation in a range of temperatures, with a maximum possible variation from -150ºC  to 180°C.

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:

a) a 5mm BBO probe head, broadband probe for direct analysis, that enables the analysis of nuclei as 1H, 13C, 51V , 19F, 31P, 15N, 17O, 33S

b) a 5mm BB probe head,  inverse broadband probe 1H / 19F

c) a 5mm DUL probe head, that enables the analysis of the nuclei 1H and 13C .

The 600 MHz system can operate with two probes and has a sample exchange unit SampleXpress for 60 samples:

a) a 5mm TXI probe with triple resonance, 1H - 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.

 

Experimental methods

The 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 - 15N .

 

Sample requirements and preparation

Samples 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 1H analysis and above 20 mg for 13C analysis. 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.


Long experiments are usually performed overnight or during the weekend.

 

The Nuclear Magnetic Resonance Laboratory at UP is part of the Portuguse NMR Network: http://ptnmr.dq.ua.pt/

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