Study Set Content:
Two common types of NMR spectroscopy are used to characterize organic structure:
1. ¹H
2. ¹³C
Used to determine the type and number of H atoms in a molecule
¹H
used to determine the type of carbon atoms in the molecule
¹³C
Chemical shifts _____ is the most commonly used form of NMR because of its
sensitivity and the large amount of structural information it yields.
Proton (1H) NMR
The chemical shift is the position on the () (in ppm) where the peak occurs
d (delta) scale
There are 3 major factors that influence chemical shifts:
○ Inductive effects by electronegative groups
○ Deshielding due to reduced electron density (due to the presence of electronegative atoms)
○ Anisotropy (due to magnetic fields generated by p bonds).
APPLICATIONS:
• A powerful technique for the characterization of the exact structure of raw materials, intermediates and finished products.
• Can determine impurities, including enantiomeric impurities, without separation, down to ca the 10% level and 1% level with two-dimensional spectroscopy.
• Can potentially be used for fingerprinting mixtures.
• Has good potential for non-destructive quantitative analysis of drugs in formulations without prior separation.
• Magnetic resonance imaging (MRI) relies on the properties of spin to obtain images.
IN SOME DRUGS:
1.Proton NMR Spectrum of Aspirin
2.Proton NMR Spectrum of Salbutamol
3.Proton NMR Spectrum of Paracetamol
4.Ibuprofen
5.Caffeine
6.Cholesterol-lowering Drugs
is an analytical tool useful for measuring the mass-to-charge ratio (m/z) of one or more molecules present in a sample.
Mass spectrometry
commonly known as mass spectroscopy, is an analytical method that uses gaseous ions sorted according to their mass-to-charge ratios in electric and magnetic fields to identify chemical compounds.
Mass spectrometry
It is a microanalytical technique requiring only a _____ of the sample to obtain characteristic information pertaining to the structure and molecular weight of analyte
few nanomoles
This technique basically studies the effect of () on molecules.
ionizing energy
provides a highly specific method for determining or confirming the identity or structure of drugs and raw materials used in their manufacture.
Mass spectrometry
It is the most accurate method of determination of the molecular mass and its molecular composition
MASS SPECTROMETRY (MS)
The best method for getting rapid identification of trace impurities, which should ideally be carried out using chromatographic separation in conjunction with high resolution mass spectrometry so that elemental compositions can be determined
STRENGTH
Mass spectrometry is not currently used in routine quality control (QC) but is placed in a research and development (R&D) environment, where it is used to solve specific problems arising from routine processes or in process development
LIMITATION
The method of choice for monitoring drugs and their metabolites in biological fluids because of its high sensitivity and selectivity.
STRENGTH
With the advent of electrospray mass spectrometry and the re-emergence of time-of-flight mass spectrometry, the technique will be of major use in the quality control of therapeutic antibodies and peptides.
STRENGTH
The instrumentation is expensive and requires support by highly trained personnel and
regular maintenance. However, these limitations are gradually being removed with
open access instruments becoming more common.
LIMITATION
1.A mass spectrometer needs to perform three functions
Creation of ions
Separation of ions
Detection of ions
