Nuclear magnetic resonance (NMR) spectroscopy is an analysis method used to determine the structure of organic compounds. Different NMR techniques include 1H NMR, 13C NMR, and two-dimensional HSQC. NMR is the definitive method for analyzing the atomic composition and structure of organic molecules.
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What is NMR analysis used for?
Nuclear magnetic resonance spectroscopy is an efficient tool in organic chemistry and quality control of different industries, as it can provide detailed information about the composition of a sample. NMR provides information about the functional groups of molecules and different isotopes of atoms. In addition, intermolecular interactions, such as small protein-ligand interactions, biomolecular dynamics, and low-transient and low-affinity complexes can be studied with NMR.
The result of, for example, a 1H NMR analysis is a spectrum with several signals corresponding to the number of chemically different types of hydrogen nuclei in the molecule. The position of these signals represents the chemical shifts, revealing what kind of chemical environment each of the nuclei is in. The relative areas under these signals (obtained by integration) tell how many hydrogen atoms of each type there are in the molecule. Lastly, the splitting pattern reveals the number of neighboring hydrogens for each individual hydrogen atom. Based on this information, a high-resolution structure of the molecule can be created.
NMR spectroscopy can be used to analyze both known and unknown compounds. Previously unknown components can be identified through comparison with established libraries of NMR spectra.
How does NMR spectroscopy work?
The principle of NMR is based on the ability of spinning nuclei to resonate with a certain magnetic field as a result of the magnetic properties of the atom's core and core electrons to survey the chemical environment of the atom. The nuclei of some atoms spin while others do not. The spinning nuclei include, for example, 1H and 13C, which can be utilized in 1H NMR and 13C NMR analyses, respectively. Other spinning nuclei can also be used, but hydrogen and carbon are the most common because of their presence in most organic compounds.
In general, all moving charged particles generate a magnetic field. When a sample containing spinning nuclei of interest is placed between the two poles of a powerful magnet in the NMR spectroscope, a strong magnetic field goes through the sample. The magnetic field causes a perturbation in the atoms, which leads to a change in the spins of their electrons.
This change in the spin is called electron relaxation, and it is unique for every element. As a result, the spinning nuclei of the atoms are charged electrically and they start to behave like magnets. Therefore, the nuclei align with or against the applied magnetic field creating an energy difference. Then, a fixed radio frequency is used to change the magnetic field to even out the energy differences. When the energies match, the nuclei can change spin states meaning they can resonate and give off a magnetic signal detected by the NMR machine. Based on the characteristic electron relaxations of elements, the structure of the molecules in the sample can be determined.
Suitable samples and sample preparation
NMR can be performed on both solid and liquid samples. Extensive sample preparation is usually not necessary: samples are just diluted to a suitable NMR solvent before analysis. Paramagnetic sample materials (ones with unpaired electrons) and large molecule sizes may cause the spectral lines to broaden to a point where the results are rendered unusable. For paramagnetic samples, EPR spectroscopy may be a more suitable method, while cryo-EM can be used to characterize large molecules.
Need an analysis?
Measurlabs offers 1H, 13C, and various 2D NMR experiments at competitive prices and fast turnaround times. You can contact our experts through the form below or at email@example.com to discuss the testing options and request a quote for your sample material.
Suitable sample matrices
- Food samples
- Fine chemicals
- Materials with NMR-active nuclei
Ideal uses of NMR spectroscopy
- Quantifying known and unknown components
- Studying molecular dynamics and interactions
- Determining the composition (types and amounts of elements) of organic samples
- Characterization of polymers, including structure, co-monomer ratios, end groups, and average molecular weight (MW)
- Sample purity determination
Frequently asked questions
NMR spectroscopy offers detailed information about the composition of organic molecules. With the method, a high-resolution structure of the molecule can be created, showing the type, quantity, and arrangement of atoms. NMR is often used in organic chemistry research and can be used as a quality control method in various other industries.
NMR samples need to be soluble in a deuterated solvent. Interpretation of the spectrum requires an experienced scientist and data collection can be time-consuming (e.g. 13C NMRs are usually run overnight).
Both solid and liquid samples are suitable for NMR analysis. Solid samples need to be soluble in a deuterated NMR solvent before the analysis. The analysis of small molecules is relatively straightforward, but it can be tricky to characterize large molecules, to a point where the signal is too weak and broad to yield valuable results.
Measurlabs offers a variety of laboratory analyses for product developers and quality managers. We perform some of the analyses in our own lab, but mostly we outsource them to carefully selected partner laboratories. This way we can send each sample to the lab that is best suited for the purpose, and offer high-quality analyses with more than a thousand different methods to our clients.
When you contact us through our contact form or by email, one of our specialists will take ownership of your case and answer your query. You get an offer with all the necessary details about the analysis, and can send your samples to the indicated address. We will then take care of sending your samples to the correct laboratories and write a clear report on the results for you.
Samples are usually delivered to our laboratory via courier. Contact us for further details before sending samples.