m pharmacy notes

1. 10/9/2019
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2. A SEMINAR ON
INSTRUMENTAION OF UV SPECTROSCOPY
By
Salunkhe Nikhil Jayvantrao
Under The Guidance Of
Dr. B. V. Udugade
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3. -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
What is spectrophotometer ?
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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
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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.
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6. TUNGSTEN LAMP
-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
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7. -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
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8. CONCLUSION
Tungsten lamp is a better source than deuterium and xenon arc
lamp because –
-Produce less noise
-It have less cost
-Greater lifetime
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9. -Monochromator
-Filters
WAVELENGTH SELECTOR DEVICE
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10. 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 .
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11. FILTERS
Filters are of four types :-
a) Absorption filters
b) Cut-off filters
c) Interference filters
d) Interference Wedges
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12. 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)%.
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13. 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.
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14. Interference filters –
• Works on the concept of wave interference.
Interference wedges-
• A wedge of dielectric of different thickness can transmit a wide
range of wavelengths.
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15. Comparison between interference filters and
absorption filters-
• The interference filters gives superior bandwidth over
absorption filters.
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16. - 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 wavelengthrange
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
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17. DETECTORS
→A detector converts a light signal into an electrical signal.
Spectrophotometers normally contain either a photomultiplier tube
detector or a photodiode detector.
Phototube: –
- Incident photon causes release of
an electron
– Not best for low-light scenarios
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18. Photomultiplier :-
– Ejected photoelectron strikes dynode,
– Result is large charge packet hitting anode
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19. Photodiodes and Photodiode arrays:–
• less sensitive
• Assembly of individual photodiodes on a Si chip
• Each diode can be addressed individually
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20. Single beam spectrophotometer
• Low in cost.
• Have high sensitivity.
• Instability due to lack of compensation for disturbance like
electronic circuit fluctuation, voltage fluctuation.
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21. Double beam spectrophotometer
• Dual-beam instruments contain more optical components which
reduces 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.
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