Nuclear Magnetic Resonance (NMR) spectroscopy
NMR spectroscopy is an analytical technique used to determine the chemical molecular structure of a compound. NMR provides both quantitative and qualitative data on the composition of a sample. This technique can be used for quality control, for research, to identify an unknown, or to determine the content and purity of a sample.
A simplified description of NMR is that the sample, dissolved in a liquid, is placed into the instrument, which contains a magnetic field. A radio frequency pulse is then sent through the sample solution in order to orient the magnetic moments of the nuclei in the solution. As the magnetic moments relax, they exhibit a free induction decay. The free induction decay is Fourier transformed into an NMR spectrum. The NMR spectrum displays chemical shifts for the individual nuclei; and from these chemical shifts, the structure of the compound can be determined.
Impact Analytical currently has a Varian 400MHz NMR System spectrometer, equipped with a broadband Pulse-Field Gradient (PFG) probe for analysis of low frequency X nuclei (15N - 31P). Typical analyses include proton and carbon-13, as well as silicon-29 and fluorine-19. The NMR also has variable temperature (-25 to 130 C) capabilities, suitable for analyzing polymers and other materials at high temperature, or monitoring chemical reactions at low temperatures. Advanced one and two-dimensional experiments, such as APT, DEPT, COSY, HETCOR, and the use of PFG, are available and necessary tools for the deconvolution of complex mixtures and materials, especially for pharmaceutical characterization.
Here is a sample NMR spectrum.