SREEKANTH NAMA, M.PHARM, (Ph.D)
DEPARTEMENT OF PHARMACY, JIMMA UNIVERISTY, HAND OUT ON COLORIMETRY 1
COLORIMETRY
Contents
•
Introduction
• Principle involved in the Colorimetry
• Colored substances
• Chemistry involved in Colorimetry
• Pharmaceutical applications
Introduction
•
It is a technique meant for measurement of color of substances. This technique also
called as visible spectroscopy.
•
In this technique the amount of light absorbed by the molecules is measured, hence it is
absorption spectroscopy.
• The energy changes that occurs at molecular level, hence it is molecular spectroscopy.
• The electrons present in the molecules undergoes excitation upon absorption of UV-
Visible radiation, hence it is electronic spectroscopy.
• Colorimetry is the technique used to determine the concentration of colored
compounds in a solution.
• Colorimetry is concern with the study of absorption of suitable radiation whose
wavelength ranges from 400-800nm.
• Any colored substance will absorb radiation in this wavelength region. Colored
substances absorbs light of different wavelength in different manner and hence we get
an absorption curve is a unique pattern for every colored solution, in this absorption
curve the wavelength at which maximum absorption of radiation takes place is called as
absorption maximum.
• This absorption maximum is characteristic or unique for every colored substance and
this is a qualitative aspect, useful to identifying the colored substance and the
absorbance is a quantitative aspect of colored compound.
•
It is very useful to measure the number of conjugated double bonds and triple bonds
(Unsaturation) and also aromatic conjugation within the various molecules.
• The extent of absorption of light in visible region governed by beers and lambert law.
SREEKANTH NAMA, M.PHARM, (Ph.D)
DEPARTEMENT OF PHARMACY, JIMMA UNIVERISTY, HAND OUT ON COLORIMETRY 2
Principle involved in the Colorimetry
When the molecule absorbs visible light, the electron