1) Gas chromatography mass spectrometry (GC-MS) is a hyphenated technique that combines gas chromatography and mass spectrometry to identify different molecules within a sample. 2) GC separates the components in a mixture through partitioning between a mobile and stationary phase, while MS identifies molecules by detecting their mass. 3) Common ionization techniques used in GC-MS include electron impact and chemical ionization. Mass analyzers like quadrupole, ion trap, and time-of-flight are used to detect ions. 4) GC-MS has applications in pharmaceutical analysis, forensics, anti-doping testing, and newborn screening for inborn errors of metabolism.

1. A CLOSER LOOK ON GC-MS
(Gas Chromatography Mass
Spectrometry)
Presented By
Ms. A.A. Bhosale (M. Pharm.)
Guided by
Dr. K. G. Bothara (Ph.D.)
STES’S SINHGAD COLLEGE OF PHARMACY
Vadgaon(Bk), Pune 411 041.

2. INTRODUCTION
Gas chromatography
Gas chromatography leads to separation of volatile organic
compounds.

3. Principle of GC
In GC the main principle of separation is partition.
The chromatographic process – partitioning
MOBILE PHASE
(gas or liquid)
Sample
in
Sample
out
STATIONARY PHASE
(solid or heavy liquid coated onto a solid or
support system)

4. In the animation below the red molecules are more soluble
in the liquid (or less volatile) than are the green molecules.

5. Distribution Coefficient
Concentration of component A in stationary phase
Concentration of component A in mobile phase
Different affinity of any 2 components to stationary phase causes the separation.

8. GC-MS – A BRIEF
•It’s a Hyphenated Technique
•Invented By James & Martin in 1952
Gas
chromatography
Mass spectrometry GC-MS
Separates
mixture of
components
into individual
Identifies
molecules
based on their
mass
A chemical analysis
technique
combining two
instruments to
provide for
powerful separation
& identification.

9. Coupling of GC to MS:
GC
Atmospheric
density heated
(200-300 ∘C)
Interfaces
MS
High vacuum
(10-6 torr)
heated
The interface b/w the GC&MS is an important role to play in the
overall efficiency of the instrument.
Both system are heated (200 -300 ∘C) both deal with compounds
in the vapor state.
Only one problem is that the atmospheric pressure output of the
GC must be reduced to vacuum of
10-5 – 10-6 torr for the MS inlet

10. Jet separator Membrane separator Effusion separator
Types of interfaces:

11. IONIZATION TECHNIQUES
1
• ELECTRON IMPACT
2
• CHEMICAL IONIZATION

12. ELECTRON IMPACT (EI)
In the Electron Impact (EI) process, electrons are emitted from a
heated filament (usually made of tungsten or rhenium) and are
accelerated across the source by using an appropriate potential
(5-100V) to achieve the required electron energy (sufficient to
ionize the molecule).
M (g) + e- M+ +
2e-

13. CHEMICAL IONIZATION (CI)
Chemical ionisation involves the ionisation of a reagent gas, such
as methane at relatively high pressure (~1 mbar) in a simple
electron impact source. Once produced, the reagent gas ions
collide with the analyte molecules producing ions through gas
phase reaction processes such as proton transfer.
nNH3 + e- NH4+ +
2e-
NH4
+ + M NH3 + [M+
H]+
NH4
+ + M [M+ NH4]+

14. Mass Analyzers
They deflects ions down a curved tubes in a magnetic fields based
on their kinetic energy determined by the mass, charge and velocity.
The magnetic field is scanned to measure different ions.
Mass analyzers
Quadrupole Ion trap Time of flight

15. Quadrupole:
In a quadrupole mass analyser a set of four rods are arranged parallel to
the direction. Here a DC current and radio frequency RF is applied to
generate oscillating electrostatic field in between the rods. Based on
this only m/z is been determined and stable oscillation takes place. And
ion travels in quadrupole axis with cork screw type of trajectory.

16. Ion trap mass analyser:
The ion trap mass analyser operates by
similar principles where it consists of
circular ring electrode
Plus two end caps that form a chamber.
Here AC or DC power along RF
potential is applied between the cups
and the ring electrode.
There the ions entering into the
chamber are trapped by
electromagnetic fields and they
oscillates in concentric trajectories.
This process is called resonant
ejection.

17. Time of flight:
 TOF mass analyser is based on simple idea that the velocities of two ions
are created by uniform electromagnetic force applied to all the ions at
same time, causing them to accelerate down a flight tube.
 Lighter ions travels faster and strike the detector first so that the m/z ratio
of ions is detected.

18. All the mass spectrometers now employ computer control of same
functions and also use a computerised display and output.
The amount of data generated even by a fairly modest mass spectrometer
is very large indeed, a single run may store data for upto 100 fragments
from each type of molecule and if, GCMS analyses is being performed, a
complete mass spectrum is generated and stored every sec for upto 90
min
DATA HANDLING

19. Pharmaceutical & other applications of GC-MS
1. Pharmaceutical applications
GC-MS analysis of urine sample know to contain cocaine.
MS spectrum of cocaineGC of cocaine

20. 2. Criminal forensics
 GC-MS can analyze the particles from a human body in order to
help link a criminal to a crime.
 GC-MS especially useful here as samples often contain very
complex matrices &results used in court.

21. 3. Sports antidoping analysis
 GC-Ms is main tool used in sports anti doping
laboratories to test athletes urine samples for prohibited
performance enhancing drugs.
Eg : anabolic steroids.

22. 4. Newborn screening (NBS)
 In born errors of metabolism are now detectable by new born
screening tests, especially the testing using GC-MS .
 It can determine compounds in urine even in minor concentration.
Disorders related to newborns:
•Amino Acid Disorders
eg. PKU.
•Fatty Acid Oxidation Disorders
• Organic Acid Disorders

23. Key References:
1. Kataria S, Beniwal p, Middha A. Gas chromatography-mass
spectrometry: applications.International Journal of Pharmaceutical &
Biological Archives, 2011; 2(6):1544-1560.
2. Patil SV, Baharete SD. Hyphenated techniques: an overview.
Journal of Pharmaceutical Research,2015; 4(2): 214-225.
3. Phalke P, Kavade S. Review on Hyphenated
Techniques.International Journal of Chemical studies, 2013; 1(3):
157-165.
4. Chatwal GR, Anand K, Instrumental methods of chemical
analysis: 2.272, 2.673.

24. ACKNOWLEDGEMENTS
I sincerely thank my guide
Dr. K. G. Bothara sir
for his constant guidance & support.
I thank our respected Principal
Dr. S. D. Sawant
& Seminar Committee for giving me
this opportunity.