in this slides contains principle and types of detectors used in Gas Chromatography. Presented by: J.Vinay Krishna. (Department of industrial pharmacy), RIPER, anantapur.

1. Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721
Detectors in Gas Chromatography
A Seminar as a part of curricular requirement for
Master of Pharmacy,
I Year - I semester
Presented by
J. Vinay Krishna
(20L81S0806)
Dept of. Industrial Pharmacy
Under the guidance/Mentorship of
Dr. Hindustan Abdul Ahad M. Pharm., PhD., FAGE
Professor & Head, Department of Industrial Pharmacy,
Program in charge (PG)

2. RIPER
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SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721
Contents:
2
 Introduction
 Principle
 Types of detectors
Conclusion
 References

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Introduction
3
A chromatography detector is a device used in gas chromatography (GC)
or liquid chromatography (LC) to detect components of the mixture being
eluted off the chromatography column. There are two general types of
detectors.
1. Destructive
2. Non-destructive.

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Destructive
A destructive detector performs continuous transformation of the column effluent
(by burning, evaporating, or mixing with reagents), with subsequent measurement
of some physical property of the resulting material (plasma, aerosol, or reaction
mixture).
Non Destructive
A non-destructive detector directly measures some property of the column effluent
(UV absorption, for example) and thus affords further analyte recovery.

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Principle of gas chromatography: The sample solution injected into the instrument
enters a gas stream which transports the sample into a separation tube known as
the "column." (Helium or nitrogen is used as the so-called carrier gas.) The various
components are separated inside the column.
Principle:

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Types of Detectors
6
 Flame Ionization Detector (FID)
 Nitrogen Phosphorus Detector (NPD)
 Electron Capture Detector (ECD)
 Thermal Conductivity Detector (TCD)
 Flame Photometric Detector (FPD)
 Photo Ionization Detector (PID)
 Electrolytic Conductivity Detector (ECD)
Mass Spectrometer (MS)

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Flame Ionization Detector (FID)
A flame ionization detector (FID) is a scientific instrument that measures
analytes in a gas stream. It is frequently used as a detector in gas chromatography.
The measurement of ion per unit time make this a mass sensitive instrument.

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Mechanism:
 Compounds are burned in a hydrogen-air flame.
 Carbon containing compounds produce ions that are attracted to the collector.
 The number of ions hitting the collector is measured and a signal is generated.
Compounds with C-H bonds. A poor response for some non-hydrogen containing
organics (e.g., hexachlorobenzene).
Sensitivity: 0.1-10 ng
Gases: Combustion - hydrogen and air; Makeup - helium or nitrogen
Temperature: 250-300°C,and 400-450°C for high temperature analyses.

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Nitrogen Phosphorus Detector (NPD)
The nitrogen–phosphorus detector (NPD) is also known as thermionic specific
detector (TSD) is a detector commonly used with gas chromatography, in
which thermal energy is used to ionize an analyte. It is a type of flame thermionic
detector (FTD), the other being the alkali flame-ionization detector (AFID).
Mechanism: Compounds are burned in a plasma surrounding a rubidium bead
supplied with hydrogen and air. Nitrogen and phosphorous containing compounds
produce ions that are attracted to the collector. The number of ions hitting the
collector is measured and a signal is generated.

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Selectivity: Nitrogen and phosphorous containing compounds
Sensitivity: 1-10 pg
Gases: Combustion - hydrogen and air;
Makeup – helium
Temperature: 250-300°C
10

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Electron Capture Detector (ECD)
An electron capture detector (ECD) is a device for detecting
atoms and molecules in a gas through the attachment of electrons via electron
capture ionization. The device was invented in 1957 by James Lovelock and is
used in gas chromatography to detect trace amounts of chemical compounds in a
sample.
Mechanism: Electrons are supplied from a 63Ni foil lining the detector cell. A
current is generated in the cell. Electronegative compounds capture electrons
resulting in a reduction in the current.

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The amount of current loss is indirectly measured and a signal is generated.
Selectivity: Halogens, nitrates and conjugated carbonyls
Sensitivity: 0.1-10 pg (halogenated compounds); 1-100 pg
(nitrates); 0.1-1 ng (carbonyls)
Linear range: 103-104
Gases: Nitrogen or argon/methane
Temperature: 300-400°C

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Thermal Conductivity Detector (TCD)
The thermal conductivity detector (TCD), also known as a katharometer, is a bulk
property detector and a chemical specific detector commonly used in gas
chromatography. This detector senses changes in the thermal conductivity of the
column eluent and compares it to a reference flow of carrier gas.
Mechanism: A detector cell contains a heated filament with an applied current.
As carrier gas containing solutes passes through the cell, a change in the filament
current occurs.The current change is compared against the current in a reference
cell. The difference is measured and a signal is generated.

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Selectivity: All compounds except for the carrier gas
Sensitivity: 5-20 ng
Linear range: 105-106
Gases: Makeup - same as the
carrier gas
Temperature: 150-250°C

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Flame Photometric Detector (FPD)
The flame photometric detector (FPD) allows sensitive and selective
measurements of volatile sulphur and phosphorus compounds.
The detection principle is the formation of excited sulphur (S2) and excited
hydrogen phosphorous oxide species (HPO) in a reducing flame.
Mechanism: Compounds are burned in a hydrogen-air flame. Sulfur and
phosphorous containing compounds produce light emitting species (sulfur at 394
nm and phosphorous at 526 nm). A monochromatic filter allows only one of the
wavelengths to pass.

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A photomultiplier tube is used to measure the amount of light and a signal
is generated. A different filter is required for each detection mode.
Selectivity: Sulfur or phosphorous containing compounds. Only one at a time.
Sensitivity: 10-100 pg (sulfur); 1-10 pg (phosphorous)
Linear range: Non-linear (sulfur); 103-105 (phosphorous)
Gases: Combustion - hydrogen and air; Makeup - nitrogen
Temperature: 250-300°C

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Photo Ionization Detector (PID)
A photoionization detector or PID is a type of gas detector. Typical photoionization
detectors measure volatile organic compounds and other gases in concentrations
from sub parts per billion to 10 000 parts per million (ppm).
Mechanism: Compounds eluting into a cell are bombarded with high energy
photons emitted from a lamp. Compounds with ionization potentials below the
photon energy are ionized. The resulting ions are attracted to an electrode,
measured, and a signal is generated.

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Selectivity: Depends on lamp energy. Usually used for aromatics and
olefins (10eV lamp).
Sensitivity: 25-50 pg (aromatics); 50-200 pg (olefins)
Linear range: 105-106
Gases: Makeup - same as
the carrier gas
Temperature: 200°C 200˚
19

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Electrolytic Conductivity Detector (ECD)
The electrolytic conductivity detector (ELCD) is a destructive, mass-sensitive
selective detector. Its main use is for regulated methods designed for
selective detection of halogen-containing compounds.
Mechanism: Compounds are mixed with a reaction gas and passed through a high
temperature reaction tube. Specific reaction products are created which mix with a
solvent and pass through an electrolytic conductivity cell. The change in the
electrolytic conductivity of the solvent is measured and a signal is generated.

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Reaction tube temperature and solvent determine which types of
compounds are detected.
Selectivity: Halogens, sulfur or nitrogen containing compounds. Only one at a
time.
Sensitivity: 5-10 pg (halogens); 10-20 pg (S); 10-20 pg (N)
Linear range: 105-106 (halogens); 104-105 (N); 103.5-104(S)
Gases: Hydrogen (halogens and nitrogen); air (sulfur)
Temperature: 800-1000°C (halogens), 850-925°C (N), 750-825°C (S)

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Mass Spectrometer (MS)
Mass spectrometry (MS) is an analytical technique that is used to measure
the mass-to-charge ratio of ions. The results are typically presented as a mass
spectrum, a plot of intensity as a function of the mass-to-charge ratio. Mass
spectrometry is used in many different fields and is applied to pure samples as well
as complex mixtures.
Mechanism: The detector is maintained under vacuum. Compounds are
bombarded with electrons (EI) or gas molecules (CI). Compounds fragment into
characteristic charged ions or fragments.

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The resulting ions are focused and accelerated into a mass filter. The
mass filter selectively allows all ions of a specific mass to pass through to the
electron multiplier. All of the ions of the specific mass are detected. The mass filter
then allows the next mass to pass through while excluding all others. The mass
filter scans stepwise through the designated range of masses several times per
second. The total number of ions are counted for each scan. The abundance or
number of ions per scan is plotted versus time to obtain the chromatogram (called
the TIC).

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Selectivity: Any compound that produces fragments within the selected mass range.
May be an inclusive range of masses (full scan) or only select ions (SIM).
Sensitivity: 1-10 ng (full scan); 1-10 pg (SIM)
Linear range: 105-106
Gases: None
Temperature: 250-300°C (transfer line), 150-250°C (source)

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Conclusion
 Most commonly used detector in the gas chromatography is Flame Ionization
Detector (FID).
 In the Gas Chromatography the gases used were Nitrogen, Helium & Hydrogen.
 Nitrogen provides the best efficiency but is extremely slow.

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References :
 Sevcik JG. Detectors in gas chromatography. Elsevier; 2011 Oct 10.
 Lovelock JE. A sensitive detector for gas chromatography. Journal of
Chromatography A. 1958 Jan 1;1:35-46.
 Selucky ML. Specific gas chromatography detectors. Chromatographia. 1971
Sep 1;4(9):425-34.
 Hartmann CH. Gas chromatography detectors. Analytical Chemistry. 1971 Feb
1;43(2):113A-25a.
27

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Thank You
28