| The principle behind this: the NUCLEUS of an atom placed in a MAGNETIC FIELD and exposed to ELECTROMAGNETIC RADIATION RESONATES at a specific frequency of that radiation. | NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY (NMR) |
| NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY (NMR)
APPLICATIONS | 1 For QUALITATIVE AND QUANTITATIVE STUDIESs of medicinal agent and other organic compounds
2 For CHARACTERIZATION OF THE EXACT STRUCTURE of raw materials and finished products
3 Can DETERMINE IMPURITIES W/OUT SEPARATION
4 NON-DESTRUCTIVE QUANTITATIVE ANALYSIS of drugs in formulation w/out prior separation
5 Potentially be used for FINGERPRINTING MIXTURES |
| NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY (NMR)
STRENGTHS
LIMITATIONS | STRENGTHS
1 Provides information about MOLECULAR STRUCTURE than any other technique
2 Results are REPRODUCIBLE
3 STABLE SYSTEM that does not need any instrument maintenance contract
LIMITATIONS
1 INSENSITIVE technique for samples ˂1 mg for proton NMR and ˂ 5 mg for carbon-13 NMR
2 EXPENSIVE instrumentation requiring SPECIALIST operator |
| NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY (NMR)
Instrumentation: | 1 Magnet w/ strong, stable, homogeneous field
2 Stable radiofrequency transmitter
3 Radio receiver and detector
4 Coil of wire surrounding the sample, w/c act as a sensor
5 Cell containing sample
6 Recorder to display absorption peaks |
| Quantitative NMR
Reference use: __
- inexpensive
- chemically unreactive
- volatile (bp, 20C) | Tetramethylsilane (TMS) |
| Quantitative NMR
Sampling: | 1. solid or liquid sample is first dissolved in solvent free of protons (CCl4, CS2, CDCl3- deuterated chloroform)
2. added to NMR sample probe
3. followed by standard TMS
Ex. assay of amyl nitrite |
| NMR
Nuclei with ODD number of neutrons and ODD number of protons have a property of __
ODD atomic mass
ODD atomic number | SPIN |
| NMR
Nuclei with __ can interact with and respond to MAGNETS | Magnetic Spin |
| NMR
1 Produced by magnets
2 Direction: | .
1 Magnetic Field
2 North to South |
| NMR
1 Without magnetic field: __
2 With magnetic field: __
- Same direction: __
- Opposite direction: __ | .
1 Random Orientation
2 Parallel Orientation
- Same direction: Lower E
- Opposite direction: Higher E |
| NMR
Nuclei in the LOWER ENERGY state can transition to the higher state by __ | Absorbing RADIOFREQUENCY EMR |
| How NUCLEAR MAGNETIC RESONANCE works? | 1 Frequency varies among nuclei
2 Depends on the strength of magnetic field
3 Depends on the CHEMICAL ENVIRONMENT of a nucleus |
| Determined by nucleus' surrounding atoms
Determined by nucleus' connectivity and relative position in a molecule | Chemical Environment |
| Chemical Environment
1 Electrons have magnetic properties it __ external magnetic field
2 Electronegative nuclei withdraw electrons: __
3 Adjacent atom of the electronegative atom is __ | ,
1 BLOCKS
2 Shielded
3 De-shielded |
| Nuclei in different chemical environments absorb radiowaves of different frequencies. TRUE OR FALSE | TRUE |
| Effect of Shielding/ De-shielding varies on nucleus __ from electronegative atom | distance |
| 1 Magnetic field causes nuclei to adopt __
2 With NO applied magentic field, all spin states are __ | 1 two spin orientations
2 degenerate |
| The frequency of RF Radiation which is absorbed induces __ which causes a PEAK to appear in the spectrum at the specific frequency | RESONANCE |
