Application of infrared spectroscopy

1. Infrared spectroscopy
❖Introduction:
Infrared spectroscopy (IR spectroscopy or vibrational
spectroscopy) is the measurement of the interaction of
infrared radiation with matter by absorption, emission, or
reflection.
Principle : The principle of infrared spectroscopy is based
upon the molecular vibrations which is further composed of
the stretching and the bending vibrations of a molecule.

2. ❖APPLICATIONS OF IR-SPECTROSCOPY IN THE ANALYSIS OF
PHARMACEUTICAL DOSAGE FORMS
➢ Determination of Aspirin, Phenacetin and Caffeine in
Tablets
Carbonyl bands (c=o) at 1764, 1511 and 1665 cm–1 for
aspirin, phenacetin and caffeine

3. ➢ Determination of Codeine Phosphate in Tablets
Determined by measuring its absorption at 942 cm–1.
➢ Determination of Meprobamate in Tablets
Band at 1582 cm–1 ( carbonyl)
❖APPLICATIONS OF IR-SPECTROSCOPY IN ANALYTICAL
CHEMISTRY
➢ DETERMINATION OF CIS-TRANS ISOMER RATIO IN
CLOMIPHENE CITRATE
➢ TO DISTINGUISH AND CHARACTERIZE THE PRI-, SEC-
AND TERT-AMINE SALTS FROM ONE ANOTHER
Amphetamine Sulphate: (primary amine salt )
Ephedrine Sulphate: (secondary amine salt) and
Quinine Hydrochloride: tertiary amine salt.
➢ IR-SPECTROSCOPY IN THE STUDY OF COMPLEX
FORMATIONS
e.g Ninhydrin complex formation studied by IR
spectroscopy

4. ➢ IR-SPECTROSCOPY IN QUANTITATIVE REACTION
SEQUENCE STUDY
Reduction of —NO2 group to —NH2 ; reduction of (c=o )
Carbonyl group to —CH (OH) ; oxidation of methyl-group
to —COOH
➢ IR-SPECTROSCOPY IN THE IDENTIFICATION OF
FUNCTIONAL GROUPS
Multifunctional compound invariably exhibit separate
absorption peaks due to presence of individual group
e.g. Amide
➢ IR-SPECTROSCOPY : IDENTIFICATION BY
FINGERPRINTING
The ‘fingerprint region’ lies between 1300-400 cm–1