HOW NMR WORKS - Chemical Analysis, Life Sciences, … NMR WORKS Nuclear magnetic resonance (NMR) is...
Transcript of HOW NMR WORKS - Chemical Analysis, Life Sciences, … NMR WORKS Nuclear magnetic resonance (NMR) is...
MAGNETIC FIELD
B1B0
TRANSMITTER
RECEIVER
GRADIENTS
SHIM POWER SUPPLY
MAGNETIC FIELD
B1B0
MAGNETIC FIELD
B1B0
01
03
04
02
Liquid Nitrogen77 Kelvin
Liquid Helium4.2 Kelvin
Superconducting Magnet4.2 Kelvin
Shim CoilsRoom Temperature
ProbeRemovable
Sample
¹H NMR SPECTRUM OF ETHANOL (CH3CH2OH)
5 4 3 2 1 0 δ(ppm)
CH2OH
CH3
STEP
STEP
STEP
STEP
Liquid Helium4.2 Kelvin
Liquid Nitrogen 77 Kelvin
Superconducting Magnet4.2 Kelvin
Shim CoilsRoom Temperature
ProbeRemovable
COMPUTER
90° RF
FID
HOW NMR WORKS Nuclear magnetic resonance (NMR) is a technique used by scientists in a broad range of disciplines—including synthetic chemistry, drug discovery and development, life science research, process monitoring, food quality and safety, petroleum discovery and production, biochemistry, and materials science—to understand molecular structure and molecular dynamics, quantify molecular species, and monitor chemical processes. Learn more at www.agilent.com/chem/nmr.
Nuclear spins in a collection of ethanol molecules after a 90˚ RF pulse.
Deliver the Radio Frequency (RF) pulses. Under the control of the host computer and VnmrJ software, the sophisticated electronics in the NMR console generate and receive RF pulses. The RF pulses are delivered to the sample via the RF coils in the NMR probe. These RF pulses generate an additional, temporary magnetic field, called B1 , which is orthogonal to the magnet’s primary B0 field. The magnetic component of the B1 field applies a torque to the nuclear spins, twisting them out of alignment with B0. Each RF pulse has a specific frequency, width, and shape, which modulates the B1 field to elicit different kinds of information from the sample.
Fourier Transform is performed to convert the FID signal to a spectrum.
Convert the FID into a spectrum. The signals detected by the probe are sent from the console to the host computer where they are converted from the time-domain into the frequency-domain through a process known as Fourier Transformation (FT). This process results in what users see as an NMR spectrum. The location, shape, and area of the signals in each spectrum provide spatial and connectivity information about the nuclei in the sample.
Nuclear spins in a collection of ethanol molecules an intermediate time after B1 is off. Free induction decay
(FID) occurs as the spins relax.
Measure the Free Induction Decay (FID). The FID is the signal produced by the sample as the
nuclear spins in the sample relax back to their original state of alignment with B0. This decay
occurs within a few seconds and is captured as a function of signal intensity versus time.
Nuclear spins at equilibrium in a collection of ethanol molecules in magnetic field B0.
Place the sample in the magnet. The sample is inserted into the center of the magnet where the homogenous magnetic field B0 aligns the spins of the nuclei in the sample. The sample
sits inside an NMR probe, and the NMR probe is surrounded by the superconducting magnet.
For Research Use Only. Not for use in diagnostic procedures.This information is subject to change without notice.
© Agilent Technologies, Inc. 2013 Printed in the USA November 1, 2013
5991-3206EN