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

GC-MS – A BRIEF

• It’s a Hyphenated Technique

• Gas Chromatography + Mass Spectroscopy

• Invented By James & Martin in 1952

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

MASS SPECTROSCOPY PRINCIPLES

1. Ion Formation

2. Ion Detection & Separation

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

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

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.

B. FLOW REGULATORS:

Used to maintain the uniform pressure and flow rate

Generally used are:

• Rotameter

• Soap Bubble Flow Meter

C. INJECTION DEVICES:

• GAS: Valve Devices

• LIQUID: Loop Devices

• SOLID: Dissolve the substance in suitable solvent and then inject.

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)

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

INSTRUMENTATION OF MASS SPECTROMETRY PART

Consists of:

• IONIZATION CHAMBERS

• MASS ANALYSERS

• DETECTORS

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

APPLICATIONS

• Fire investigation

• Drug analysis

• Explosive analysis

• Environmental analysis

• Drug Abuse Analysis

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