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INSTRUMENTATION OF UV
SPECTROPHOTOMETER
-PRANAV KUMAR SINGH
M.Sc.- Applied Chemistry
(Third semester)
What is spectrophotometer ?
- A device used for measuring transmittance and
absorbance of a sample as a function of wavele...
Source
Wavelength
Selector
Device
Sample
DetectorReadout
Block Diagram→
SOURCES
Characterstics of an ideal source-
- Gives constant intensity
- Have low noise
- Prolonged stability
Types of UV-V...
DEUTERIUM ARC LAMP
- It is a low pressure gas discharge light source.
- Works on the principle of molecular emission.
- Wa...
Advantages-
-Yields good intensity continuum
-Provides intensity in UV region and useful intensity in the visible
region
-...
-Works on the principle of black body radiation.
-It is a spatially and temporarily incoherent source
-Wavelength range – ...
Advantages-
-Yields good intensity continuum.
-Provides intensity over a part of the UV region and over the entire
part of...
-Generates light by passing current through a gas (Xe) under
very high pressure.
-Wavelength range – (200 – 1000) nm.
-Lif...
Advantages–
-Yields good intensity continuum.
-Provides intensity over the entire UV and visible region.
-Ruggedness – goo...
Tungsten lamp is a better source than deuterium and xenon arc
lamp because –
-Produce less noise
-It have less cost
-Great...
-Monochromator
-Filters
WAVELENGTH SELECTOR DEVICE
Monochromator
• Function – to produce a beam of monochromatic (single
wavelength) radiation that can be selected from a wi...
- By rotating prism or
grating we can get
the light of desired
wavelength.
Comparison between prism
and grating –
- Dispersion given by prism is
angularly non linear and temprature
sensitive while ...
FILTERS
Filters are of four types :-
a) Absorption filters
b) Cut-off filters
c) Interference filters
d) Interference Wedg...
Absorption Filters –
• They are made up of coloured glass
or dye .
• Transmit only a specific band
of wavelength.
• They a...
Cut-off filters-
• Transmission is about 100%.
• Used to achieve only a specific band
of wavelength.
• They are used in co...
Interference filters –
• Works on the concept of wave interference.
• The thickness of the dielectric and reflectivity of the metallic
films are carefully selected because these factors cont...
Interference wedges-
• A wedge of dielectric of different thickness can transmit a wide
range of wavelengths.
• By choosin...
Comparison between interference filters and
absorption filters-
• The interference filters gives superior bandwidth over a...
- Sample containers are generally made up of
plastic, quarts and glass.
• Plastic cuvette- used for fast spectroscopic
ass...
DETECTORS
→A detector converts a light signal into an electrical signal. Ideally, it
should give a linear response over a ...
Photomultiplier :-
– Ejected photoelectron strikes dynode, secondary e- released
– Voltage accelerates e- to next dynode a...
Photodiodes and Photodiode arrays :–
Reverse biased junction
– Photons produce e-- hole pairs α current
– Current α Plight...
Single beam spectrophotometer
• Low in cost.
• High energy throughput due to non splitting of source beam.
• Have high sen...
Double beam spectrophotometer
• Dual-beam instruments contain more optical components which
reduces throughput and sensiti...
APPLICATION
1. Detection of Impurities- UV absorption spectroscopy is one of the
best methods for determination of impurit...
Detection of Impurities
UV absorption spectroscopy is one of the best methods for
determination of impurities in organic m...
ACKNOWLEDGEMENT
I wish to express my sincere gratitude to Mrs. Jyoti Panday for
providing me an opportunity to do my prese...
Thank you
for your attention
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Instrumentation of uv spectrophotometer pranav kumar singh

introduction of UV spectrophotometer.

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Instrumentation of uv spectrophotometer pranav kumar singh

  1. 1. INSTRUMENTATION OF UV SPECTROPHOTOMETER -PRANAV KUMAR SINGH M.Sc.- Applied Chemistry (Third semester)
  2. 2. What is spectrophotometer ? - A device used for measuring transmittance and absorbance of a sample as a function of wavelength of E.M.R. Components of spectrophotometer→ - Source - Wavelength selector Device - Sample Container - Detector - Read out
  3. 3. Source Wavelength Selector Device Sample DetectorReadout Block Diagram→
  4. 4. SOURCES Characterstics of an ideal source- - Gives constant intensity - Have low noise - Prolonged stability Types of UV-Visible sources- - Deuterium Arc Lamp - Tungsten lamp - Xenon Arc Lamp
  5. 5. DEUTERIUM ARC LAMP - It is a low pressure gas discharge light source. - Works on the principle of molecular emission. - Wavelength range→ (190-420)nm - Life time approx 2000hrs.
  6. 6. Advantages- -Yields good intensity continuum -Provides intensity in UV region and useful intensity in the visible region -Produce low noise Disadvantages- -Don’t have prolonged stability
  7. 7. -Works on the principle of black body radiation. -It is a spatially and temporarily incoherent source -Wavelength range – (350 – 3000) nm -Lifetime approx 10000 hrs TUNGSTEN LAMP
  8. 8. Advantages- -Yields good intensity continuum. -Provides intensity over a part of the UV region and over the entire part of the visible region. -Produce low noise. Disadvantages- -Have poor assembly which can cause mechanical damage through impact or vibration. -Evaporation and condensation of tungsten filament causes blackening of glass surface.
  9. 9. -Generates light by passing current through a gas (Xe) under very high pressure. -Wavelength range – (200 – 1000) nm. -Lifetime – (500 – 4000) hrs. XENON ARC LAMP
  10. 10. Advantages– -Yields good intensity continuum. -Provides intensity over the entire UV and visible region. -Ruggedness – good to very good. Disadvantages– -Audible noise – higher. -Requirement of high voltage for initiation. -Generate significant heat and need external cooling.
  11. 11. Tungsten lamp is a better source than deuterium and xenon arc lamp because – -Produce less noise -It have less cost -Greater lifetime CONCLUSION
  12. 12. -Monochromator -Filters WAVELENGTH SELECTOR DEVICE
  13. 13. Monochromator • Function – to produce a beam of monochromatic (single wavelength) radiation that can be selected from a wide range of wavelengths. • Components – - Entrance slit . - Collimating device (to produce parallel light ). - Dispersing device (grating , prism). - A focusing lens or mirror . - An exit slit .
  14. 14. - By rotating prism or grating we can get the light of desired wavelength.
  15. 15. Comparison between prism and grating – - Dispersion given by prism is angularly non linear and temprature sensitive while the dispersion given by grating is angularly linear and temprature insensitive . - Dispersion is high in grating as compaired to prism .
  16. 16. FILTERS Filters are of four types :- a) Absorption filters b) Cut-off filters c) Interference filters d) Interference Wedges
  17. 17. Absorption Filters – • They are made up of coloured glass or dye . • Transmit only a specific band of wavelength. • They are inexpensive. • Transmission is only about (10-20)%.
  18. 18. Cut-off filters- • Transmission is about 100%. • Used to achieve only a specific band of wavelength. • They are used in combination with absorption filters to decrease the bandwidth of the absorption filters.
  19. 19. Interference filters – • Works on the concept of wave interference.
  20. 20. • The thickness of the dielectric and reflectivity of the metallic films are carefully selected because these factors control the transmitted wavelength. • The transmitted radiation will have very narrow bandwidth.
  21. 21. Interference wedges- • A wedge of dielectric of different thickness can transmit a wide range of wavelengths. • By choosing the correct position on the wedges , variable bandwidths of about 20 nm can isolated.
  22. 22. Comparison between interference filters and absorption filters- • The interference filters gives superior bandwidth over absorption filters. • Greater the bandwidth the lower the transmittance % through that filter .
  23. 23. - Sample containers are generally made up of plastic, quarts and glass. • Plastic cuvette- used for fast spectroscopic assays, where speed is more important than high accuracy. • Glass cuvette- used in the wavelength range of visible light. - transmission range 340-2000nm • Quartz cuvettes- they are of two types- → UV quartz- most common material. - transmission range 190-2500 nm → IR quartz- rarely used - transmission range 190-3500 nm - Smallest capacity holding- 70 microliter - Largest capacity holding- 2.5ml or larger SAMPLE CONTAINER
  24. 24. DETECTORS →A detector converts a light signal into an electrical signal. Ideally, it should give a linear response over a wide range with low noise and high sensitivity. Spectrophotometers normally contain either a photomultiplier tube detector or a photodiode detector. Phototube: – - Incident photon causes release of an electron – Photocurrent α Plight – Not best for low-light scenarios
  25. 25. Photomultiplier :- – Ejected photoelectron strikes dynode, secondary e- released – Voltage accelerates e- to next dynode and so on • big voltage divider – Result is large charge packet hitting anode
  26. 26. Photodiodes and Photodiode arrays :– Reverse biased junction – Photons produce e-- hole pairs α current – Current α Plight • less sensitive • Assembly of individual photodiodes on a Si chip • Each diode can be addressed individually
  27. 27. Single beam spectrophotometer • Low in cost. • High energy throughput due to non splitting of source beam. • Have high sensitivity. • Instability due to lack of compensation for disturbance like electronic circuit fluctuation, voltage fluctuation, mechanical components instability or drift in energy of light sources.
  28. 28. Double beam spectrophotometer • Dual-beam instruments contain more optical components which reduces throughput and sensitivity. • The more complex mechanical design of the dual-beam spectrophotometer may result in poorer reliability. • Instability factors due to lamp drift, stray light, voltage fluctuations do not affect the measurement.
  29. 29. APPLICATION 1. Detection of Impurities- UV absorption spectroscopy is one of the best methods for determination of impurities in organic molecules. 2. Structure elucidation of organic compounds- UV spectroscopy is useful in the structure elucidation of organic molecules, the presence or absence of unsaturation, the presence of hetero atoms. 3. Quantitative analysis- UV absorption spectroscopy can be used for the quantitative determination of compounds that absorb UV radiation. 4. Qualitative analysis- UV absorption spectroscopy can characterize those types of compounds which absorbs UV radiation. Identification is done by comparing the absorption spectrum with the spectra of known compounds.
  30. 30. Detection of Impurities UV absorption spectroscopy is one of the best methods for determination of impurities in organic molecules. Additional peaks can be observed due to impurities in the sample and it can be compared with that of standard raw material. By also measuring the absorbance at specific wavelength, the impurities can be detected. Benzene appears as a common impurity in cyclohexane. Its presence can be easily detected by its absorption at 255 nm.
  31. 31. ACKNOWLEDGEMENT I wish to express my sincere gratitude to Mrs. Jyoti Panday for providing me an opportunity to do my presentation work on “UV Spectrophotometer” I sincerely thank Mrs. Jyoti Panday for their guidance and encouragement in carrying out this presentation work. I also wish to express my gratitude to my class friends of BBAU, who rendered their help during the period of my presentation work. .
  32. 32. Thank you for your attention

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