Introduction
Spectroscopy methods [1,2]
It is the branch of science dealing with the study of interaction
between Electromagnetic radiation and matter. It is a most powerful
tool available for the study of atomic and molecular structure/s and
is used in the analysis of wide range of samples. Optical spectroscopy
includes the region on electromagnetic spectrum between 100 Å and
400 μm. The regions of electromagnetic spectrum are shown in table 1.
Ultraviolet-Visible spectrophotometry [3]
UV-Visible spectrophotometry is one of the most frequently
employed technique in pharmaceutical analysis. It involves measuring
the amount of ultraviolet or visible radiation absorbed by a substance
in solution. Instrument which measure the ratio, or function of ratio, of
the intensity of two beams of light in the U.V-Visible region are called
Ultraviolet-Visible spectrophotometers.
In qualitative analysis, organic compounds can be identified by use
of spectrophotometer, if any recorded data is available, and quantitative
spectrophotometric analysis is used to ascertain the quantity of
molecular species absorbing the radiation. Spectrophotometric
technique is simple, rapid, moderately specific and applicable to
small quantities of compounds. The fundamental law that governs the
quantitative spectrophotometric analysis is the Beer -Lambert law.
Beer’s law: It states that the intensity of a beam of parallel
monochromatic radiation decreases exponentially with the number of
absorbing molecules. In other words, absorbance is proportional to the
concentration.
Lambert’s law: It states that the intensity of a beam of parallel
monochromatic radiation decreases exponentially as it passes through
a medium of homogeneous thickness. A combination of these two laws
yields the Beer-Lambert law