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The topic of
spectrophotometry will be
explored through the
fundamental principles
of spectrophotometry,
including how molecules
absorb light in relation to
their concentration
and the role of
instruments like
spectrophotometers
in measuring absorbance.
We will discuss the
Beer Lambert law,
the relationship
between absorbance,
concentration and
solution properties,
and why calibration and
wavelength selection
are crucial for accuracy.
The lecture will also highlight
common applications in biology,
such as nucleic acid and
protein quantification,
as well as key limitations and
practical steps to improve
measurement reliability.
Spectrophotometry is a
cornerstone analytical technique
in chemistry and biology,
enabling the quantification
of how much a substance
absorbs light at a
specific wave length.
The method is based
on the principle that
molecules absorb
light in relation to
their concentration by
measuring the intensity of
transmitted light
and comparing it to
the initial intensity,
absorbance is determined.
This concept is vital for
measuring protein and
DNA concentrations and
monitoring enzyme kinetics,
as each molecule absorbs light
best at specific wavelengths.
To measure absorbance reliably,
we use a spectrophotometer,
an instrument
designed to produce,
select, and detect
light efficiently.
Key components include
a light source,
usually a tungsten
or deuterium lamp,
a monochromter or filter
to isolate the
desired wave length,
a sample holder or cuvette,
and a detector to quantify
transmitted light.
