UV-Visible Detector:-
UV-visible detectors are commonly used in analytical
chemistry to detect and quantify the presence of molecules that absorb UV or
visible light. These detectors work based on the principles of absorbance and
transmittance of light.
UV-visible detectors typically consist of a light source, a
sample cell or flow cell, and a detector. The sample is passed through the
cell, which is usually made of a clear material such as quartz or glass, and
then exposed to the light source, which emits UV or visible light depending on
the application.
When the light passes through the sample, some of it is
absorbed by the molecules present in the sample, while the rest of it is
transmitted through the sample. The detector measures the intensity of the transmitted
light and compares it to the intensity of the light source. The amount of light
absorbed by the sample is directly proportional to the concentration of the
absorbing molecules in the sample.
The detector generates a signal based on the difference
between the intensity of the light source and the intensity of the transmitted
light. This signal is then processed and analyzed to determine the
concentration of the absorbing molecules in the sample.
UV-visible detectors are commonly used in a variety of
applications, such as in pharmaceuticals, environmental analysis, and forensic
sciences, to detect and quantify the presence of molecules such as proteins,
DNA, and pollutants.
Categorization of UV
light range:
UV light is
part of the electromagnetic spectrum, which consists of a range of different
wavelengths of light. UV light has a shorter wavelength than visible light, and
is therefore higher in energy.
The range of
UV light is usually divided into three regions, based on their wavelength and
energy:
UVA (315-400
nm): This is the longest wavelength range of UV light and has the lowest
energy. UVA light is also known as "black light" and is commonly used
in applications such as curing adhesives and coatings, and in the entertainment
industry for creating fluorescent effects.
UVB (280-315
nm): This range of UV light has a higher energy than UVA light and is
responsible for causing sunburn and skin damage. It is also used in medical and
industrial applications such as phototherapy for treating skin conditions and
sterilizing surfaces.
UVC (100-280
nm): This range of UV light has the highest energy and is the most damaging to
living organisms. UVC light is typically filtered out by the Earth's
atmosphere, but is used in sterilization processes for water and air
purification, and in medical and laboratory settings for sterilizing equipment
and surfaces.
It is
important to note that prolonged exposure to any type of UV light can be
harmful to human health, and appropriate safety measures should be taken when working
with UV light.
UV light range used in HPLC analysis:
In HPLC
(high-performance liquid chromatography), UV lights are commonly used to detect
and quantify analytes in a sample. The UV light used in HPLC is typically in
the range of 190-400 nm, which covers both the UVA and UVB regions of the UV
spectrum.
The most
commonly used wavelength in HPLC is 254 nm, which is in the UVC range but can
still be used safely as it is filtered out by the sample cell and does not
reach the detector. Other common wavelengths used in HPLC include 210 nm, 220
nm, 280 nm, and 365 nm, depending on the specific application and the analytes
being detected.
UV light is
absorbed by molecules with certain chromophores, such as double bonds, carbonyl
groups, and aromatic rings, which makes it a useful tool for detecting and
quantifying analytes in a sample. The amount of light absorbed is proportional
to the concentration of the absorbing species in the sample, and this
information is used to generate a chromatogram that can be used for qualitative
and quantitative analysis.
Visible light range used in HPLC
analysis:
Visible light
is part of the electromagnetic spectrum and has wavelengths between 400-700 nm.
In HPLC, visible light is not typically used as a detection method because most
analytes do not strongly absorb visible light. However, some specialized
applications may use visible light detection for specific analytes or compounds
that have absorption in the visible range.
One example
of the use of visible light detection in HPLC is in the analysis of
carotenoids, which are natural pigments that give fruits and vegetables their
orange, yellow, and red colors. Carotenoids absorb light in the visible range,
and therefore can be detected using visible light detection in HPLC.
In general,
UV detection is the most commonly used detection method in HPLC due to its high
sensitivity and specificity. Other detection methods such as fluorescence and
electrochemical detection may also be used in HPLC, depending on the specific
application and the analytes being detected.
Abhishek Singh is the author of Pharma technical support. He is pharmaceutical professionals, having experience of more than 12 years in Quality.