Detectors used in UV spectophotometry

1. DETECTORS USED IN
GAS CHROMATOGRAPHY
PRESENTED BY:
NIMMI ROY
1ST YEAR MPHARM
DEPT OF PHARMACEUTICS
SCP , VALACHIL
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2. CONTENTS
• Introduction
• Instrumentation
• Detectors
– Definition
– Ideal characters
– Type of detectors
– Thermal conductivity detector
– Flame ionization detector
– Nitrogen phosphorous detector
– Flame photometric detector
– Electron capture detector
– Atomic emission detector
• References
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3. Gas chromatography:
• Introduction:
It is process of separating components(s) from the given crude
drug by using a gaseous mobile phase . It is mainly used for
the separation of thermally stable and volatile organic and
inorganic compounds.
Two types:
1.GSC- Mobile phase is gas and stationary phase is soild adsorbent.
2.GLC- Mobile phase is gas and stationary phase is non-volatile
liquid bound to solid support.
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4. Instrumentation
• Six basic components
1. Carrier gas
2. Sample injection system
3. Thermostated chamber
4. The separation column
5. One or more detectors
6. An amplification and recorder system
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6. DETECTORS
The detector which is situated at the exit of the separating
column , is to sense and measure the small amount of
separated components present in the carrier gas stream leaving
the column.
The output of the detector is fed to a device which
produces a trace called chromatogram.
The choice of the detector which depends upon factors such as:
a) Concentration level to be determined
b) The nature of the separated components
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7. Ideal characters of detector
1. Adequate sensitivity.
2. Good stability and reproducibility.
3. A linear response to solutes.
4. A temperature range from room temperature to at least 400°C.
5. A short response time that is independent of flow rate.
6. Similarity in response towards all solutes.
7. Non destructive of sample.
8. It should respond to wide variety of compound.
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8. Type of detector:
•Based on specificity:
Non specific
i. Thermal conductivity detector
ii. Atomic emission detector
iii. Photo ionization detector
 Specific
i. Flame ionization detector
ii. Flame photometry
iii. Nitrogen phosphorous detector
iv. Electron capture detector
v. Nitrogen chemiluminescence
detector
•Based on destructivity:
Destructive
i. Flame ionization detector
ii. Nitrogen phosphorus
detector
iii. Photo ionization detector
iv. Nitrogen
chemiluminescence
detector
 Non destructive
i. Thermal conductivity
detector
ii. Electron capture detector
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9. Thermal conductivity detector
• It is also called as Katharometer or Hot wire detector.
• It works on the principle of Wheatstone bridge.
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10. Application:
These are having large temperature co-efficient of resistance and
corrosion resistance.
Thermistors are used for some trace elements
The following figure which shows the wheatstone bridge:
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11. Flame ionization detector:
• The FID was invented by scientist Harley and Pretorius and
separated by MCWilliams and Dewer.
• It makes the use of an oven , wherein a flame is produced burning
hydrogen gas in presence of oxygen of air.
Fig:1 Fig:2
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12. Nitrogen phosphorous detector
• A nitrogen phosphorus detector is a relatively simple
modification to the interior of FID , it may be made much
more sensitive to either nitrogen or phosphorus containing
compounds.
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13. Flame photometric detector
• A third generation type of flame detector is flame photometric
detector , also based on standard FID.
• It is selective towards compound containing Sulphur and
phosphorous
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14. Electron capture detector
• It responds to only those compounds whose molecules have an
affinity for electrons.
• Eg: chlorinated compound, unsaturated compound etc.ry ve
• On the other side , it responds very little to compounds such as
hydrocarbons.
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15. Atomic emission detector
•The strength of the detector
lies in its ability to
simultaneously determining
elements.
•It uses microwave energy to
excite molecules.
•This emits radiation which
breaks down molecules to
atoms such as , S , N , P , Hg ,
etc
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16. References
1.Skoog, west.et.al. “fundamentals of analytical
chemistry”,8th edition , page no.950
2.Sharma B.K,” Instrumental methods of analysis”,
6th edition , page no.128
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17. THANK YOU
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