Nuclear Magnetic Resonance Spectroscopy
Nuclear Magnetic Resonance (NMR) spectroscopy is an analytical technique used to determine the chemical structure of a compound. NMR provides quantitative and qualitative data on the composition of a sample.
A simplified description of the technique is that the sample is submitted in a deuterated solvent and transferred into an NMR tube. The sample NMR tube is placed into 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 a 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 broad band 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.