Detectors in all types of analytical techniques

1. Detectors
Analytical Chemistry
(CHEM- 211 )
BS-Chemistry-5 semester
Amna Dilshad
BWSC-18-40
Govt. Postgraduate College for women Sahiwal

2. 1.Detectors
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3. 2.Ideal Detector
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4. 3..Types of detectors
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5.  Photon detectors
• Photon detectors count photons of light. A
photon detector has some surface that absorbs photons and
produces some effect (current, voltage) proportional to the
number of photons absorbed.
• Examples are photovoltaic cells , phototube etc.
• A photovoltaic cell consists of a layer of semiconductor (like
selenium , Hg-Cd-Te , Cu2O, etc.) sandwiched between two
metallic electrodes, with the exposed electrode thin enough
to be transparent. Photons of light are absorbed by the
semiconductor, forming electrons and holes that create a
current proportional to the number of photons absorbed.

6.  Thermal detectors
A thermal detector absorbs radiation and
changes temperature. Because the power in
absorbed radiation is typically rather small
(<10-7 W), the detector itself should be small
so that it has a low heat capacity.
Examples are thermocouples ,bolometer
,Golay detector and pyro electric detector etc.
 A thermocouple is the joining of two dissimilar-metal or metal alloy
wires or films.When this occurs, a potential difference is formed
between the other ends of the metals. Since potential differences
are temperature-dependent (called the Seebeck effect),
temperature values or changes in temperatures can be determined
by calibration.

7. 4.Use of detectors
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8. 5.Detectors in GC
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9. Flame ionization
detector
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 𝑂𝑟𝑔𝑎𝑛𝑖𝑐 𝑐𝑜𝑚𝑝. +𝐻2 + 𝑂2 → 𝐶𝑜𝑚𝑏𝑢𝑠𝑡𝑖𝑜𝑛 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 + 𝐻2𝑂 + 𝑖𝑜𝑛𝑠 + 𝑟𝑎𝑑𝑖𝑐𝑙𝑠 + 𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑛𝑠
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10. Thermal conductivity detector
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11. Electron capture detector
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13. 6.Detectors in Hplc
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15. UV-Vis detector
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16. Refractive index detector
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17. Electrical conductivity detector
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18. Electrochemical detector
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19. 7.Detectors in spectrometry
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20. Barrier layer cell/photovoltaic cell.
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21. Barrier layer cell
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23. Phototube/photoemissive tubes
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26. Photomultiplier tubes
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30. 8.Conclusion
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31. 9.References
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32. ThankYou
-Amna Dilshad