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Materials Technology can offer competitive NMR testing and interpretation as part of our routine analytical suite.
Nuclear Magnetic Resonance is a very sensitive analytical technique that detects the magnetic properties of hydrogen nuclei i.e. protons and hence the term Proton NMR or 1H-NMR.
Protons have certain magnetic properties and hence when a magnetic field is applied to them they respond to that applied field by aligning with the field. If the magnetic field is oscillated the protons will flip from one direction to the other. As there is a certain energy associated with this flip it is possible to detect this flip by measuring the interaction with the applied field. The result is a peak in a graph which is associated with the flip and is called the resonance condition.
Typical NMR spectrum
The energy required to make the proton flip will vary depending on the local environment that the proton is in or the groups it is attached to. Hence, CH3 protons will behave differently to CH2 protons. As a result of this it is possible to produce a spectrum of proton resonance versus chemical shift (ppm). The shift is indicative of the specific group of protons and the resonance is proportional to the concentration of groups.
Hence, NMR is a useful technique for determining the chemical structure of materials or confirming the identity of unknown species or contaminants. Integration of the peaks and comparison with a known reference can ascertain quantitative measurements for compositions. It is a technique that is most useful when applied with other techniques. It can also be used in factory environments for quality control purposes but these are often very simplified machines that are not intended for analytical purposes.
GC/MS combines the features of gas-liquid chromatography and mass spectrometry to identify different substances within a test sample. Applications of GC-MS include drug detection, fire investigation, environmental analysis, explosives investigation, and identification of unknown samples. Because of its very sensitive nature it can be used to detect very small concentrations of contaminants within samples. For this reason great care must be taken when handling the samples.
Typical GCMS spectrum
The GC-MS has been widely heralded as a "gold standard" for forensic substance identification because it is used to perform a specific test. A specific test positively identifies the actual presence of a particular substance in a given sample. A non-specific test merely indicates that a substance falls into a category of substances. Although a non-specific test could statistically suggest the identity of the substance, this could lead to false positive identification.
The test can be use quantitatively and qualitatively, however, quantitative analysis requires the preparation of suitable reference and calibration samples.
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