The document provides a comprehensive overview of various gas chromatography detectors, including their operating principles, selectivity, and applications. It covers detectors such as the flame ionization detector, nitrogen phosphorus detector, electron capture detector, and mass spectrometer, detailing how they generate signals based on solute interactions. Additionally, the document lists references for further reading on the subject.

1. Prepared by:
Aditya Sharma
M.S. (Pharm)
Pharmaceutical Analysis
NIPER Guwahati
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GAS
CHROMATOGRAPHY
DETECTORS

2. CONTENTS
• Introduction
• Flame Ionization Detector
• Nitrogen Phosphorus Detector
• Electron Capture Detector
• Thermal Conductivity Detector
• Flame Photometric Detector
• Photoionization Detector
• Mass Spectrometer
• Conclusion
• References
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3. INTRODUCTION
• As solutes elute from the column, they interact with the detector. The detector converts this
interaction into an electronic signal that is sent to the data system. The magnitude of the signal is
plotted versus time (from the time of injection) and a chromatogram is generated.
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Classification of
Detectors
General-Purpose Detectors
Flame Ionization Detector
Thermal Conductivity
Detector
Selective, High-Sensitivity
Detectors
Nitrogen Phosphorus
Detector
Electron Capture Detector
Mass Spectrometer
Flame Photometric Detector
Figure 1: Classification of Detectors

4. FLAME IONIZATION DETECTOR (FID):
• 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.
• Selectivity: Compounds with C-H bonds. A poor
response for some non-hydrogen containing
organics (e.g., hexachlorobenzene).
Figure 2: Flame Ionization Detector
Reference:https://www.shimadzu.com/an/service-support/technical-support/analysis
basics/fundamentals/detector.html. Accessed on 21/02/2021. 4

5. NITROGEN PHOSPHORUS DETECTOR (NPD):
• 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.
• Selectivity: Nitrogen and phosphorous containing
compounds.
Figure 3: Nitrogen Phosphorus Detector
Reference:https://www.shimadzu.com/an/service-support/technical-support/analysis
basics/fundamentals/detector.html. Accessed on 21/02/2021. 5

6. ELECTRON CAPTURE DETECTOR (ECD):
• 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. The amount
of current loss is indirectly measured and a signal is
generated.
• Selectivity: Halogens, nitrates and conjugated
carbonyls.
Figure 4: Electron Capture Detector
Reference:https://www.shimadzu.com/an/service-support/technical-support/analysis
basics/fundamentals/detector.html. Accessed on 21/02/2021. 6

7. THERMAL CONDUCTIVITY DETECTOR (TCD):
• 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.
• Selectivity: All compounds except for the carrier
gas.
Figure 5: Thermal Conductivity Detector
Reference:https://www.shimadzu.com/an/service-support/technical-support/analysis
basics/fundamentals/detector.html. Accessed on 21/02/2021.
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8. FLAME PHOTOMETRIC DETECTOR (FPD):
• 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. 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.
Figure 6: Flame Photometric Detector
Reference:https://www.shimadzu.com/an/service-support/technical-support/analysis
basics/fundamentals/detector.html. Accessed on 21/02/2021. 8

9. PHOTOIONIZATION DETECTOR (PID):
• 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.
• Selectivity: Depends on lamp energy. Usually used
for aromatics and olefins (10 eV lamp).
Figure 7: Photoionization Detector
Reference:https://www.shimadzu.com/an/service-support/technical-support/analysis
basics/fundamentals/detector.html. Accessed on 21/02/2021.
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10. MASS SPECTROMETER (MS):
• The detector is maintained under vacuum. Compounds are bombarded with electrons or gas
molecules.
• Compounds fragment into characteristic charged ions or fragments. The resulting ions are
focused and accelerated into a mass filter which selectively allows detection of all ions of a
specific mass to pass through to the electron multiplier.
• The mass filter then allows the next mass to pass through while excluding all others. 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.
• A mass spectrum is obtained for each scan which plots the various ion masses versus their
abundance or number.
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11. CONCLUSION
Detector Type Support Gases Selectivity Detectability Dynamic range
Flame Ionization Detector Mass Flow Hydrogen and air Most organic
compounds
100 pg 107
Thermal Conductivity Detector Concentration Reference Universal 1 ng 107
Electron Capture Detector Concentration Make-up Halides, nitrates, nitriles,
peroxides, anhydrides,
organometallics
50 fg 105
Nitrogen Phosphorus Detector Mass Flow Hydrogen and air Nitrogen, phosphorus 10 pg 106
Flame Photometric Detector Mass Flow Hydrogen and air
possibly oxygen
Sulphur, phosphorus,
tin, boron, arsenic,
germanium, selenium,
chromium
100 pg 103
Photoionization Detector Concentration Make-up Aliphatics, aromatics,
ketones, esters,
aldehydes, amines,
heterocyclics,
organosulphurs, some
organometallics
2 pg 107
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12. REFERENCES
• Poole, C., 2015. Ionization-based detectors for gas chromatography. Journal of Chromatography A, 15(8),
1421, pp.137-153.
• Eiceman, G., Gardea-Torresdey, J., Overton, E., Carney, K. and Dorman, F., 2002. Gas Chromatography.
Analytical Chemistry, 74(12), pp.2771-2780.
• Selucky, M., 1971. Specific gas chromatography detectors. Chromatographia, 4(9), pp.425-434.
• Adlard, E. and Juvet, R., 1975. A Review of Detectors for Gas Chromatography Part I: Universal Detectors. C R
C Critical Reviews in Analytical Chemistry, 5(1), pp.03-13.
• Guiochon, G. and Guillemin, C., 1990. Gas chromatography. Review of Scientific Instruments, 61(11),
pp.3317-3339.
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