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Proton and Carbon NMR service

TU Dublin - Tallaght Campus offers a Proton and Carbon NMR service, using its JEOL Lambda NMR system – operating at 300 MHz (1H-NMR) and 75 MHz (13C-NMR).

  • The instrument is normally operated at ~20 ºC, but its Variable Temperature facility can work in the range –100 to +150 ºC.
  • The following experiments are routine:
  • 1H-spectrum: with peak pick, integration, automatic expansion of multiplets;
  • standard resolution = 0.18 Hz/0.0006 ppm;
  • D2O shake: repeat 1H-spectrum after treatment with D2O, to identify exchangeable H’s;
  • 13 C-spectrum (proton-decoupled): with peak pick;
  • standard resolution = 0.6 Hz/0.008 ppm;
  • DEPT-90 & DEPT-135 spectra: displayed with 13C-spectrum in stacked plot
  • (allows easy identification of types of carbon: Cq, CH, CH2, CH3);
  • HH-COSY 2D spectrum (allows easy identification of 1H-1H coupling);
  • CHSHIFT 2D spectrum (also known as "CH HETCOR";
  • allows easy identification of CH connectivity).

A wide range of specialised experiments can be run by arrangement; please ask for details.

Samples are typically run in solution in deuterochloroform, but a range of other solvents are available: D2O, CD2Cl2, acetone-d6, DMSO-d6, methanol-d6, F3CCOOD, etc.

Results are typically printed on A4 paper (A3 if required), with fully experimental and processing details. Spectra are also retained on computer disk for 3 weeks, in case you need to ask for further processing or printouts after you see the results. (This time can be extended by arrangement).
 

Procedures, Requirements for Sample Submission
The following is a guide to the amount of sample required:

1H-NMR: ~10 mg (spectrum will typically be run with ~3-5 mg, made up in ~700 ml of solvent). Considerably more dilute samples can be run, but require longer running times, and experiments become very long with <0.2mg.

13C-NMR (incl. DEPT, CHSHIFT): at least 1 mg for every non-equivalent carbon.

For example, N,N-dibutylaniline [PhN(CH2CH2CH2CH3)2] has 8 non-equivalent carbons, so it must be soluble to at least 8 mg/700 ml (i.e. ~12 mg/ml) in the intended solvent. Such a solution will give 1H-, 13C-, DEPT, HH- & CH-2D spectra with reasonably short scanning times. Ideally, at least 20 mg should be supplied, to allow for a repeat spectrum, should it be necessary.

Other points to note on Sample Submission:
Solubility should be tested in advance using the non-deuterated counterpart of the intended solvent (for VT-NMR, check over intended temperature range)
Samples should be submitted dry in air-tight containers (solutions will be prepared by the NMR service, with a reference compound for 1H-NMR, as appropriate)
Put your reference number securely on the sample and the same reference number on the Sample Submission Sheet
To ensure that we can confirm arrival of your sample at TU Dublin - Tallaght Campus and its timely processing, please leave a brief voicemail message on 01-4042612 when submitting samples by post

Special Requirements:
The normal expectation is that a sample submitted will be a single compound in a pure state. If this is not the case (e.g. where the integration of the relative amounts of a two-compound mixture is required), please give as much information as possible
Similarly, if the sample is unavoidably impure, please provide as much information as possible about the likely impurities (we maintain extensive spectral libraries of common organic chemicals, so if we know your impurity, we may also know where its peaks are likely to show up)
Please ensure to include full details about sample sensitivity (temperature, air, water, light, etc.), if relevant
If you intend to deliver a sensitive compound which requires immediate special storage (e.g. low temperature) or needs to be run immediately, contact us in advance
The submission of highly hazardous or potentially highly hazardous chemicals should be cleared in advance with Dr. Brian Murray or Dr. Bernie Creaven.
Similarly, provide full details about any special processing requirements (expansions, spectral areas of particular interest, Hz peak pick, etc.): requesting such detail after the spectrum has been run will typically result in delay
Samples will not normally be returned (if you required unused portion, or unused portion plus recovery of sample from solution, please specify)

Interpretation of Spectra:
The NMR Service does not provide a spectral interpretation service. Dr. Brian Murray and/or Dr. Bernie Creaven may be able to provide this by arrangement.
We occasionally provide training courses. It may also be possible to arrange admittance to the appropriate lectures of one of our full-time or part-time undergraduate courses.

 

NMR @ TU Dublin - Tallaght Campus

Brian A. Murray
NMR Spectroscopy is a major tool in analytical chemistry, and the Institute acquired a Jeol 300 MHz instrument in 1995. It is one of the college’s most expensive individual instruments, but also one of the most useful.

NMR stands for Nuclear Magnetic Resonance, and involves aligning the ‘spin’ of the nucleus of an atom (which behaves like a mini-magnet) by putting a sample in a strong magnetic field. The effect is similar to the way a compass needle aligns itself with the Earth’s field. The ‘spin’ can also be flipped by putting in energy (like turning a compass needle away from north). We use radio frequency just beyond the FM band to do this, hence the ‘300 MHz’ in the name.

When an unknown substance is studied, each type of nucleus shows a distinctive signal characteristic of its environment, allowing the substance to be identified. At the moment, we can look at hydrogen and carbon atoms, two elements that are abundant in organic chemicals, foodstuffs, pharmaceuticals, and biochemicals. An imminent upgrade will extend the elements we can look at to include boron, nitrogen, silicon, and phosphorus.

The instrument has had a major impact on undergraduate teaching, being used in over a dozen modules in chemistry and biology. Chemistry students are introduced to NMR in their diploma year. They enhance their skills during degree studies, identifying multi-functional organic compounds, supporting their "detective work" with other analytical techniques – e.g. infra-red and mass spectroscopy – and test-tube tests. NMR spectrometers are widely used in research, and are appearing more in industry as well, so our graduates are well prepared by such study.

The ready availability of sophisticated NMR techniques also has a major impact on the scope of our own research, and on our ability to compete for external funding. Postgraduate students and post-doctoral fellows routinely use the instrument, often as part of research funded as part of the NCSR (National Centre for Sensors Research), a joint DCU-ITT initiative supported by the Higher Education Authority.

Not everyone needs their own NMR. As part of the Institute mission to assist local small- to medium-sized enterprises, we also offer a commercial service, "NMR ITT!", with rapid sample turnaround. A similar service at a reduced rate is offered to bona fide external academic customers.

The instrument is jointly managed by Drs. Brian Murray and Bernie Creaven. A robotic sample system allows high throughput and "24/7" operation: the system often runs continuously for weeks at a time. A Variable Temperature facility allows experiments between –100 and +150 °C.

Further details on the external service are available from Brian (brian.murray@it-tallaght.ie; 01-4042811).


 

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