Gas chromatography detectors
- 1. Gas Chromatography Detectors Presented by :- Anurag S Tadkase RCPIPER, Shirpur, Dhule Guided by :- Dr . P . M . Jain
- 2. Content….. • Introduction • Ideal characteristics of detectors • Classification of G C Detectors • Flame ionization detector (FID) • Thermal Conductivity Detectors (TCD) • Barrier discharge ionization detector (BID) • Conclusion • Viva-voce
- 3. • Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition (Thermally Stable). • Gas Chromatography is Firstly Carried out in Austria by AT James & Martin (1952) • It is type of Column Chromatography • Non Lc separation • Gas is used as mobile phase hence called as Gas Chromatography Introduction
- 4. G C Detectors • 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: Destructive and Non- Destructive. • The Destructive detectors perform continuous transformation of the column effluent (burning, evaporation or mixing with reagents) • The Non-destructive detectors are directly measuring some property of the column eluent (for example UV absorption) and thus affords greater analyte recovery.
- 5. Ideal characteristics of detectors • Sensitivity should lie in the range 10-8 to 10-15 g/ml • It should respond rapidly • It should respond to a wide variety of compounds • Good stability and reproducibility • It should produce linear response to the concentration of solutes in the eluate • A temperature range from room temperature to at least 400 degree C • Non destructive to the sample
- 6. Classification of G C Detectors Based on Destructive & Non- Destructive Destructive • Flame ionization detector (FID) • Barrier discharge ionization detector (BID) • Flame thermionic detector (FTD) • Flame photometric detector (FPD) Non-Destructive • Thermal Conductivity Detectors (TCD) • Electron capture detector (ECD)
- 7. Classification of G C Detectors Based on General purpose detectors & Selective Detectors General purpose Detector • Flame ionization detector (FID) • Thermal Conductivity Detectors (TCD) • Barrier discharge ionization detector (BID) Selective High-Sensitivity Detectors • Electron capture detector (ECD) • Flame thermionic detector (FTD) • Flame photometric detector (FPD) • Sulphur chemiluminescence detector (SCD)
- 8. Flame Ionization Detectors (FID) • The FID was invented by scientist Harley and Pretorious. • The FID is the most common detector used in gas chromatography. • The FID is sensitive to, and capable of detecting, compounds that contain carbon atoms (C), which accounts for almost all organic compounds. • However, the FID is not sensitive to carbon atoms with a double bond to oxygen, such as in carbonyl groups and carboxyl groups (CO, CO2, HCHO, HCOOH,etc.).
- 9. Flame Ionization Detectors (FID) • The FID was invented by scientist Harley and Pretorious • The FID is the most common detector used in gas chromatography. • The FID is sensitive to, and capable of detecting, compounds that contain carbon atoms (C), which accounts for almost all organic compounds. • However, the FID is not sensitive to carbon atoms with a double bond to oxygen, such as in carbonyl groups and carboxyl groups (CO, CO2, HCHO, HCOOH,etc.).
- 10. Flame Ionization Detectors (FID) • The FID creates a hydrogen flame by burning air and hydrogen supplied from below. • The carbon in a sample carried into the detector on carrier gas(N2 ) is oxidized by the hydrogen flame, which causes an ionization reaction. • The ions formed are attracted by a collector electrode to an electrostatic field, where the components are detected
- 11. Flame Ionization Detectors (FID) • The FID creates a hydrogen flame by burning air and hydrogen supplied from below. • The carbon in a sample carried into the detector on carrier gas(N2 ) is oxidized by the hydrogen flame, which causes an ionization reaction. • The ions formed are attracted by a collector electrode to an electrostatic field, where the components are detected
- 12. Flame Ionization Detectors (FID) • The FID creates a hydrogen flame by burning air and hydrogen supplied from below. • The carbon in a sample carried into the detector on carrier gas(N2 ) is oxidized by the hydrogen flame, which causes an ionization reaction. • The ions formed are attracted by a collector electrode to an electrostatic field, where the components are detected
- 13. Flame Ionization Detectors (FID) • The FID creates a hydrogen flame by burning air and hydrogen supplied from below. • The carbon in a sample carried into the detector on carrier gas(N2 ) is oxidized by the hydrogen flame, which causes an ionization reaction. • The ions formed are attracted by a collector electrode to an electrostatic field, where the components are detected Application • Organic compound analysis Detection Limit • 0.1 ppm
- 14. Advantages • Minute amount of solute can be detected • Gives linear response • As it responds to the number of C-atoms entering the detector per unit time, it is mass sensitive rather than concentration sensitive • Insensitive towards water, CO2, SO2, NO2 Disadvantage • More complicated and more expensive • Destruction of the sample • Functionals groups like carbonyl, alcohol, halogen, amine are not detected
- 15. Thermal Conductivity Detectors (TCD) • It works on the principle of Wheatstone's bridge. It is also known as Katharometer • The TCD can detect all compounds other than the carrier gas. • The TCD is mainly used to detect inorganic gas and components that are not sensitive to the FID • Helium is commonly used as a carrier gas. (N2 and Ar are used to analyze He and H2.) Application • Water vapor, formaldehyde, formic acid, etc. • Analysis of compounds not detectable by the FID Detection Limit • 10 ppm
- 16. The TCD detects Sample by reading the change in filament temperature caused by the difference in thermal conductivity between the carrier gas and sample components. Schematic Diagram of theTCD
- 17. The Wheatstone bridge works on the principle of null deflection, i.e. the ratio of their resistances are equal and no current flows through the circuit. Under normal conditions, the bridge is in the unbalanced condition when current flows through the galvanometer. • When only the carrier gas is flowing at a constant flowrate -Each filament maintains a constant temperature and a constant voltage is produced between C and D. • when sample is passed from detector. -A change in filament temperature occurs, which -Changes the resistance value, and -Changes the voltage between C and D
- 18. TCD Analysis Example When the thermal conductivity of the analytical target component is lower than the carrier gas, the TCD reads an elevation in filament temperature. Conversely, when the thermal conductivity of the analytical target component is higher than the carrier gas, the TCD reads a decrease in filament temperature. When the Thermal Conductivity of the Analytical Target Component is Lower than the Carrier Gas V=IR
- 19. TCD Analysis Example When the thermal conductivity of the analytical target component is lower than the carrier gas, the TCD reads an elevation in filament temperature. Conversely, when the thermal conductivity of the analytical target component is higher than the carrier gas, the TCD reads a decrease in filament temperature. Selection by Analytical Objective Decreases
- 20. Advantages • TCD is simple, rugged, inexpensive • Non destructive to the sample • Gives accurate results Disadvantage • It has low sensitivity • Detection of organic compounds using N2 or Co2 as carrier gas is less sensitive.
- 21. Barrier Discharge Ionization Detectors (BID) • The BID is Shimadzu’s proprietary detector that can detect all inorganic and organic compounds other than He and Ne. • The BID is also capable of detecting trace amounts of impurities at the ppm level that the TCD failed to detect during an inorganic gas analysis. Applications •Organic compound analysis •Trace gas analysis Detection Limit • 0.05 ppm
- 22. The principle of detection used by the BID is as follows. • The BID generates a stable He plasma, uses the energy emitted by the excited He to ionize compounds, then attracts these ions to a collector. • The He plasma energy emitted is extremely high and capable of ionizing all compounds other than He, which is used to create the plasma, and Ne, which has extremely high ionization energy. • As a result, the BID can detect any compound, in principle, other than He and Ne.
- 23. The principle of detection used by the BID is as follows. • The BID generates a stable He plasma, uses the energy emitted by the excited He to ionize compounds, then attracts these ions to a collector. • The He plasma energy emitted is extremely high and capable of ionizing all compounds other than He, which is used to create the plasma, and Ne, which has extremely high ionization energy. • As a result, the BID can detect any compound, in principle, other than He and Ne.
- 25. Principle of Ionization • Compounds eluted from the column are ionized by light energy from the plasma. • Ions are attracted to the collection electrode and output as peaks. • The light energy from the He plasma is 17.7 eV (electron volts), which is extremely high. • The BID is capable of high-sensitivity detection of all compounds other than the plasma gas He, and Ne, which has a higher ionization energy than He.
- 26. Detector Detectable Compound Detection Limit FID Organic compounds (other than formaldehyde and formic acid) 0.1 ppm TCD All compounds other than the carrier gas 10 ppm BID All compounds other than He and Ne 0.05 ppm ECD Organic halogen compounds Organic metal compounds 0.1 ppb FTD Organic nitrogen compounds Inorganic and organic phosphorus compounds 1 ppb 0.1 ppb FPB Inorganic and organic sulfur compounds 10 ppb Tabular Representation
- 28. The Choice of Mobile Phase Carrier Gas is Depend onWhich Type of Detector we are using in our Instrument (GC) Sr No Carrier Gas Detector 1 N2 FID 2 He TCD 3 He BID
- 29. Viva-Voce Which detector is used to detect formaldehyde, formic acid ? A) FID B)TCD
- 30. Viva-Voce Which detector is used to detect formaldehyde, formic acid ?
- 31. THANK YOU