1. Department of Quality Assurance TECHNIQUES
AFFILIATEDBY SAVITRIBAI PHULEPUNEUNIVERSITY
SSR CollegeOf Pharmacy, Saily– Silvassa
U. T. Of Dadra & Nagar Haveli – 396230, India.
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2. INTRODUCTION
• GC-MS is a hyphenated method- The combination of separation power of GC with
the detection power of MS.
• It was successfully accomplished by Holmes and Morrell in 1957.
• Produces pure fractions from your sample
• Capable of separating, detecting and particularly
characterizing the organic compound particularly when present
in small quantity.
Gas
chromatograph
• Yields qualitative information about a pure compound
• Provides some definite structural information from in small
quantity.
Mass-
spectrometer
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3. WHY IS IT COMBINED ?
• GC can separate volatile and semi-volatile compounds with great
resolution, but it cannot identify them.
• MS can provide detailed structural information on most compounds
such that they can be exactly identified, but it cannot readily separate
them.
• In both techniques, the sample is in the vapor phase, and both techniques
deal with about the same amount of sample .
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4. PRINCIPLE OF GC-MS
The sample solution is injected into the GC inlet where it is vaporized
and swept onto a chromatographic column by the carrier gas.
The sample flows through the column and the compounds comprising
the mixture of interest are separated by virtue of their relative interaction
with the coating of the column (stationary phase) and the carrier gas
(mobile phase).
The latter part of the column passes through a heated transfer line and
ends at the entrance to ion source where compounds eluting from the
column are converted to ions.
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5. INSTRUMENTATION
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6. COMPOSITION OF GC-MS
The GC-MS is composed of three major building blocks:
1. Gas chromatograph
2. Interface
3. Mass spectrometer
gas chromatograph
The gas chromatograph utilizes a capillary column which depends on the
column's dimensions (length, diameter, film thickness) as well as the phase
properties (e.g. 5% phenyl polysiloxane). The difference in the chemical
properties between different molecules in a mixture will separate the
molecules as the sample travels the length of the column. 6

7. INTERFACE
After separation of our sample components by the GC,
we need a way of introducing it into our MS - an
interface.
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Interface:
The interphase between the GC and MS has an important role to play in overall
efficiency of the instrument:
It must be capable of providing an inert pathway from the column to the ion sources
without loss of chromatographic resolution.
Removing the carrier gas.
Reducing the pressure from about one atmosphere at the column outlet to 10-5 – 10-6
mmhg in the ion source.

8. MASS SPECTROMETER:
• Electron ionization is most commonly used to produce ions from the
compounds separated by the GC. Chemical ionization may also be
used. Quadrupole, ion trap, and time-of flight analyzers may be used
to separate ions in the MS. These analyzers have rapid response
times and relatively low costs.
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9. ADVANTAGES:
• Fast and inexpensive.
• Efficient and high resolution.
• Sensitive- ppb-ppm.
• Non-destructive sample recovery
possible.
• Small sample size.
• Simple and reliable mechanism
DISADVANTAGES:
• Only compounds with vapour pressure
about exceeding 10 torr.
• Determining positional substituents on
aromatic rings is often difficult.
• If MS feed is poor it results in
background noise in the mass spectrum.
• Certain isomeric compounds cannot be
determined by mass spectrometer.
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10. APPLICATIONS
1. Environment studies: GC-MS is becoming the tool of choice for tracking organic pollutants in the
environment. Most organic analysis of environmental samples, include many major classes of
pesticides.
2. Law enforcement: GC-MS is increasingly used for detection of illegal narcotics.
3. Food analysis : GC-MS is extensively used for the analysis of these compounds which include
esters, fatty acids, alcohols, aldehydes, terpenes etc. It is also used to detect and measure
contaminants from spoilage or adulteration which may be harmful.
4. Medicine: Dozens of congenital metabolic diseases also known as Inborn error of metabolism are
now detectable by newborn screening tests, especially the testing using gas chromatography–mass
spectrometry. GC-MS can determine compounds in urine even in minor concentration.
5. Criminal forensics: It is also commonly used in forensic toxicology to find drugs and/or poisons in
biological specimens of suspects, victims, or the deceased.
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11. REFERENCES
1. Gas Chromatography-Mass Spectrometry; By Ronald A. Hites Indiana University School
of Public and Environmental Affairs and Department of Chemistry
2. Fundamental GC-MS introduction; http://www.chromaacademy.com.
3. Wiley interscience series in mass spectrometry; Instrumentation, Interpretation and
Application.
4. http://www.scientific.org/tutorials/articles/gcms.html
5. http://en.wikipedia.org/wiki/GCMS
6. Principles of instrumental analysis; by skoog, hollrer, nieman; 5th edition; page no: 528,
718-720.
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12. THANK YOU
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