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A CLOSER LOOK ON GC-MS [GAS CHROMATOGRAPHY- MASS
SPECTROSCOPY]
BY
SUBHRADIP ROYCHOWDHURY* & SATARUPA BHATTACHARJEE**
*M.PHARM 2ND SEMESTER DEPT. OF PHARM. SC. B.I.T., MESRA-835215
**B.PHARM 8TH SEMESTER GURU NANAK INSTITUTE OF PHARMACEUTICAL SCIENCE & TECHNOLOGY, KOLKATA
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GC-MS – A BRIEF
• It’s a Hyphenated Technique
• Gas Chromatography + Mass Spectroscopy
• Invented By James & Martin in 1952
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GAS CHROMATOGRAPHY PRINCIPLES
• May be Gas Liquid [GLC] or Gas Solid Chromatography [GSC] but GLC is preferred
• GLC works by partition but GSC works by adsorption
• In GLC the substance to be studied first converted to gas which works as the mobile phase
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MASS SPECTROSCOPY PRINCIPLES
1. Ion Formation
2. Ion Detection & Separation
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ION FORMATION
• Techniques used to form ions are:
1. Electron Ionisation
2. Chemical Ionisation
3. Desorption Ionisation
i. Secondary Ion Mass Spectroscopy [SIMS]
ii. Fast Atom Bombardment [FAB]
iii. Matrix Associated Laser Desorption Ionisation [MALDI]
4. Electrospray Ionisation
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ION SEPARATION AND DETECTION
4 types of instruments are used:
i. Direct Focusing Type:
a) Single Focusing
b) Double Focusing
ii. Quadruple Mass Analyser
iii. Quadruple Mass Storage
iv. Time Of Flight Mass Analyser
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INSTRUMENTATION OF GAS CHROMATOGRAPHY
A. CARRIER GAS:
• Chemically inert
• Suitable for the detector use
• Amount of impurity should be less
• Easily available and should be cheap
• Non inflammable
Generally used carrier gases are He, H, N, Ar etc.
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B. FLOW REGULATORS:
Used to maintain the uniform pressure and flow rate
Generally used are:
• Rotameter
• Soap Bubble Flow Meter
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C. INJECTION DEVICES:
• GAS: Valve Devices
• LIQUID: Loop Devices
• SOLID: Dissolve the substance in suitable solvent and then inject.
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D. COLOUMNS:
Columns can be of the following types:
• Packed Columns [Stationary Phase- PEG]
• Open Tubular Column or Open Capillary Column/ GOLAY Coloumn
• SCOT ( Support Coated Open Tubular Column)
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E. TEMPERATURE CONTROLLING DEVICES:
The devices are very important role playing. Generally used Temperature Controlling Devices are:
• PRE HEATERS (For Vapour Formation)
• THERMOSTATICALLY CONTROLLED OVEN
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INSTRUMENTATION OF MASS SPECTROMETRY PART
Consists of:
• IONIZATION CHAMBERS
• MASS ANALYSERS
• DETECTORS
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PRINCIPLE OF WORKING AND INTERFACES
GC-MS works by
1. ISO THERMAL PRINCIPLE
2. LINER PRINCIPLE
Interfaces of GC MS are
3. Molecular Separator
4. Permeation Separator
5. Open Split
6. Capillary Direct
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APPLICATIONS
• Fire investigation
• Drug analysis
• Explosive analysis
• Environmental analysis
• Drug Abuse Analysis
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REFERENCE
• Silverstein R; Spectroscopic Identification Of Organic Compounds; Wiley Publication Delhi; 6th Edition; 2009; Page 2-70
• Skoog D et al; Fundamentals of Analytical Chemistry; Cengage Brain Publication London; 9th Edition; 2010; Page 16-25
• Kemp W; Organic Spectroscopy; Palgrave Macmillan Limited London UK; 1991; Page 72-75
• mtweb.mtsu.edu/nchong/MS%20Ion%20Sources-Ryan-6200.ppt cited on 11.02.2014