-Techniques-

Nuclear Magnetic Resonance (NMR) Spectroscopy

Nuclear magnetic resonance 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. Nuclear magnetic resonance spectroscopy 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, usually 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 chemical molecular structures of the compound can be determined.

Capabilities

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
Silicon-29 and Fluorine-19

Capable of analyzing a wide range of nuclei. Notables include phosphorus, boron, carbon, silicon, nitrogen. Some Applications for liquid NMR include the following (there are some limitations in terms of sample types, most organics are suitable):

Identity confirmation.
Purity Assay.
Identification of unknowns.
Structure elucidation.
Emulsion droplet size measurement.
Measurement of diffusion coefficients.

Available Types of Sequences:

1D with option of pre-saturation to suppress strong signals.
2D Homonuclear correlations.

The nuclear magnetic resonance spectroscopy 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 are available and necessary tools for the deconvolution of complex mixtures and materials, especially for pharmaceutical characterization.

These include: