Answer / ananth

PDA - Photo diode array

UV- Ultra violet


with use of PDA detector, we can measure the area or height
of particular peak at different wavelengths ranging from
200 to 800 nm by injecting the solution at once. Where as
in uv detector we can measure the area or height of the
peak only at two different wavelengths. But that
wavelengths also to be selected before injecting the
solution.

Answer / fathy

There are three types of UV detectors, fixed wavelength,
variable wavelength and diode array. The fixed types use a
lamp which emits at a certain wavelength. Mercury vapor
lamps are probably the most common and emit intense light at
253.7 nm. Because of the intensity of the radiation, fixed
wavelength detectors can be up to 20 times more sensitive
than variable wavelength detectors. Compounds containing
carbonyl groups, multiple double bonds, or aromatic rings
can be detected at this wavelength.
The variable types use a deuterium or similar lamp that
produces a broad spectrum of wavelengths that are separated
by a diffraction grating. A diffraction grating consists of
a large number (15,000 – 30,000 per inch) of very fine
groves etched into a high polished surface. The grating
works like a prism but generally the resolving power is
higher for gratings than for prisms. The light from the
grating is reflected to a barrier containing a tiny slit.
The instrument is adjusted so that only the wavelength of
interest passes through the slit. The selected wavelength
is passed through the sample. Some of the light is absorbed
by the sample and the amount passing through the sample is
measured and is proportional to the concentration of the
absorbing compound.
Fixed and variable spectrophotometers select a single
wavelength of light to pass through the sample. On the
other hand, the photodiode array detector passes a wide
spectrum of light through the sample and then the light is
separated into individual wavelengths after passing through
the sample. The spectrum of light is directed to an array of
photosensitive diodes. Each diode can measure a different
wavelength which allows for the monitoring of many
wavelengths at once. Most typically, only one or two
wavelengths are monitored during a chromatographic run.
Monitoring two peaks instead of one can provide information
on the purity of the peak, or it can be used to quantify a
peak when an interfering peak is present.

Answer / alpesh patel (jbcpl)

PDA - Photo diode array detector

UV- Ultra violet detector

Including above answers, the main difference between PDA &
UV detector is that we can calculate peak purity in PDA
detector only which helps us to confirm that the only
single impurity comes at perticular retention time.

Answer / t jagadeeswara reddy

PDA Detector- by using this detector we can analyse the
unknown sample(whose wave length was not known) in the range
of 190 to 800nm.


UV Detector- By using this we can analyse the sample(whose
wave length was known) by fixing its wavelength to the
particular value.

Answer / amit agrawal (torrent res.)

in ultra violet detector, you cn only analyse the compound
at particular wavelength you selected but in photo diode-
array detector, you can select multiple of wavelength due
to presence of polychromator (wavelength between 190-380nm)
and hence peak purity identification is also carried out
due to this property.

Answer / dnyaneshwar

In uv analysis you can analyse your sample at 4 differnt
wavelenth (depending on the make of HPLC instrument) in pda
analysis you can analyse your sample in the range of 190nm
to 800nm

Answer / k.vineel kumar

PDA is that in which one can observe the merging of the
peaks that means the peak purity but which is not possible
in case of UV detector.

Answer / prerna

PDA - Photo diode array detector

UV- Ultra violet detector


with the use of PDA detector, we can measure the area ,
height of particular peak at different wavelengths ranging
from 200 to 800 nm by injecting the solution at once in
three dimension form (3D).

So that we can scann that sample from 190 to 800 nm range.


Where as in uv detector we can measure the area and height
of the peak only at one wavelength. But that wavelength
must be selected before injecting the solution.

Answer / rajib hazarika

1. By PDA detector, we can measure the area/height
of particular sample at wavelengths ranging from
190 to 800 nm by a single injection( 3D scan is possible(Response Vs time Vs wavelength). Whereas in uv detector scanning is not possible.)
2. for unknown sample with unknown lambda maximum with a single injection PDA we can determine the lambda maximum but by UV several injection is required with different wavelength.
(for method validation, process validation, Research and development PDA is prefered as compared to UV
3. If proper elution is established with the help of multi step gradient mobile phase and column then analysis of mixture of compounds(with different Lambda max) can be possible by a single injection in PDA.

Answer / nirav

In PDA you select & adjust wave length as actual, but in UV
you must know the wave length of your product.

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