Gas chromatography

Gas chromatography

1. GAS CHROMATOGRAPHY BY:- DEEPAK RAVI ME student

2. CONTENTS CHROMATOGRAPHY DIFFERENT TECHNIQUES OF CHROMATOGRAPHY GAS CHROMATOGRAPHY REQUIREMENT FOR GAS CHROMATOGRAPHY BLOCK DIAGRAM OF GAS CHROMATOGRAPHY QUALITATIVE ANALYSIS ADVANTAGES AND DISADVANTAGES OF GAS CHROMATOGRAPHY MODERN APPROACH

3. CHROMATOGRAPHY Laboratory technique for the separation of a mixture. The mixture is dissolved in a fluid called the mobile phase, which carries it through a structure holding another material called the stationary phase.  The various constituents of the mixture travel at different speeds, causing them to separate. The separation is based on differential partitioning between the mobile and stationary phases. Chromatograph: equipment that enables a sophisticated separation, e.g. gas chromatographic or liquid chromatographic separation. Chromatogram : Visual output of the chromatograph. In the case of an optimal separation, different peaks or patterns on the chromatogram correspond to different components of the separated mixture.

4. TECHNIQUES BASED ON CHROMATOGRAPHIC BED SHAPE Column chromatography : Separation technique in which the stationary bed is within a tube.  Planar chromatography : S eparation technique in which the stationary phase is present as or on a plane. The plane can be a paper, serving as such or impregnated by a substance as the stationary bed ( paper chromatography ) or a layer of solid particles spread on a support such as a glass plate ( thin layer chromatography )

5. TECHNIQUES BASED ON PHYSICAL STATE OF MOBILE PHASE Gas chromatography (GC): Also known as gas-liquid chromatography, (GLC), a separation technique in which the mobile phase is a gas.  Gas chromatographic separation is always carried out in a column, which is typically "packed" or "capillary" . Liquid chromatography (LC): Separation technique in which the mobile phase is a liquid. carried out either in a column or a plane

6. GAS CHROMATOGRAPHY Gas chromatography: Mobile phase a carrier gas, usually an inert gas such as helium or an nonreactive gas such as nitrogen. Hydrogen is preferred for improved separations.  The stationary phase is a microscopic layer of liquid or polymer on an inert solid support, inside a piece of glass or metal tubing called a column. The instrument used to perform gas chromatography is called a gas chromatograph. The gaseous compounds being analysed interact with the walls of the column, which is coated with a stationary phase. This causes each compound to   elute  at a different time, known as the  retention time  of the compound. The comparison of retention times is what gives GC its analytical usefulness.

7. CONTINUED…. The function of the stationary phase in the column is to separate different components, causing each one to exit the column at a different time(retention time). As the carrier gas sweeps the analytic molecules through the column, this motion is inhibited by the adsorption of the analytic molecules either onto the column walls or onto packing materials in the column. The rate at which the molecules progress along the column depends on the strength of adsorption, which in turn depends on the type of molecule and on the stationary phase materials.

8. CONTINUED…… Since each type of molecule has a different rate of progression, the various components of the analytic mixture are separated as they progress along the column and reach the end of the column at different times(retention Time). Detector: used to monitor the out let stream from the column; thus, the time at which each component reaches the outlet and the amount of that component can be determined. Generally, substances are identified(qualitatively) by the order in which they emerge(elute) from the column and by the retention time of the analytic in the column.

9. REQUIREMENT FOR GAS CHROMATOGHRAPHY VOLATILITY:- Tendency of a substance to evaporate at normal temperatures POLARITY:- Substance comprised of molecules that contain unbalanced localized charges (dipoles) is a polar substance.  Polar substances tend to interact with other polar substances and rarely react to a significant degree with nonpolar substances When two atoms form a covalent bond, they each share an electron. Different atoms have different abilities to attract electrons quantified by their electronegativity values. When one atom in a covalent bond has a much higher electronegativity than the other, the electron is found closer to that atom than the weaker one. This creates a dipole effect with a slight negative charge at the atom the electron favours and a slight positive charge at the other

10. BLOCK DIAGRAM OF GAS CHROMATOGRAPHY

11. COMPONENT OF GAS CHROMATOGRAPH carrier gas flow regulator injector column stationary phase oven detectors display device

12. CARRIER GAS he(common), others:n2,h2 safety; non-flammability, cost and efficiency are factors for gas selection inertness suitable for the detector high purity easily available

13. FLOW METER Deliver the gas with uniform pressure/flowrate Flowmeters:- Rotameter

14. INJECTOR Transfers the sample into the column. Provides the means to introduce a sample into a continuous flow of carrier gas. Injectors are usually heated to ensure sample’s transfer to a gas phase. Volatile liquid or gaseous sample is injected through a septum.

15. COLUMN Gas chromatography columns : packed and capillary. Packed columns :A glass or stainless steel coil (typically1-5m total length and 5mm inner diameter) , filled with the stationary phase, or a packing coated with the stationary phase. Capillary columns: A thin fused-silica (purified silicate glass) capillary (typically10-100 m in length and 0.5 mm inner diameter) that has the stationary phase coated on the inner surface. Provides much higher separation efficiency than packed columns but are more easily overloaded by too much sample. The main chemical attribute regarded when choosing a column is the polarity of the mixture, The polarity of the sample must closely match the polarity of the column stationary phase to increase resolution and separation while reducing runtime.

16. TEMPERATURE CONTROL DEVICES Temperature Control Devices Preheaters: convert sample into its vapour form, present along with injecting devices Thermostatically controlled oven Temperature maintenance in a column is highly essential for efficient separation.

17. STATIONARY PHASES For every polar sample, polyethylene glycol( thickess 0.25mircometer) is commonly used as the stationary phase. Stationary Phases must have: 1.Low volatility 2.Thermal stability 3.Chemical inertness

18. SOME STATIONARY PHASE LIST

19. DETECTOR Placed at the exit of the column. Employed to detect and provide a quantitative measurement of the various constituents of the sample The choice of a particular type of detector is governed by the following factors : High sensitivity, sufficient enough to provide adequate signal for even small sample Response should be linear, unaffected by temperature and flowrate. Non distorted shape of peak and non destructive. Detector temperature must not condense the eluted vapours in it. Simple & Inexpensive Applicable to wide range of samples Good reproducibility, rapidity and linearity .

20. COMMONLY USED DETECTOR Most commonly used types:- 1.Thermal Conductivity Detector TCD 2.Flame Ionization Detector FID 3.Electron Capture Detector ECD 4.Atomic-Emission Detector AED 5.Flame Photometric GC Detector FPD

21. QUALITATIVE ANALYSIS Chromatographic data is presented as a graph of detector response(y-axis) against retention time(x-axis), which is called a chromatogram. This provides a spectrum of peaks for a sample representing the analytics present in a sample eluting from the column at different times. The number of components in a sample is determined by the number of peaks. The amount of a given component in a sample is determined by the area under the peaks. The identity of components can be determined by the given retention times.

22. ADVANTAGES AND DISADVANTAGES OF GC ADVANTAGES:- High Resolution Very high sensitivity, detect down to 100 ppm. Very good precision and accuracy. Very good separation Time(analysis is short), fast analysis is possible. Small sample is needed-ml Good detection system Quantitatively analysis DISADVANTAGES :- Sample must be volatile Dirty sample choke the capillary

23. MODERN APPROACH GCMS:- Gas Chromatography Mass Spectrometry Mass spectrometry: Analytical technique that ionizes chemical species and sorts the ions based on their mass-to-charge ratio.  Gas chromatography–mass spectrometry (GC-MS): Analytical method that combines the features of gas-chromatography and mass spectrometry to identify different substances within a test sample. Applications of GC-MS include drug detection, fire investigation, environmental analysis, explosives investigation, and identification of unknown samples

24. GCMS:-GAS CHROMATOGRAPHY MASS SPECTROMETRY

25. 2014 IEEE International Conference on Liquid Dielectrics, Bled Slovenia, June 30 - July 3, 2014 M ethanol Detection in Transformer Oils using Gas Chromatography and Ion Trap Mass Spectrometer S. Y. Matharagel , Q. Liul , E. Davenportl , G. Wilson2, D. Walker3 and Z.D. Wang The University of Manchester, Manchester, M13 9PL, UK 2The National Grid Company, Warwick, CV34 6DA, UK 3Scottish Power, Blantyre, G72 OHT, UK

26. Continued….. Abstract- Paper ageing is an irreversible process, which has made paper insulation a lifetime determining factor for transformers. Chemical indicators in oil such as carbon oxide gases and 2-FAL, are used to indicate the ageing state of paper as it is difficult to obtain paper samples to measure DP or tensile strength. Methanol amount in oil was recently found to be an early-ageing indicator for paper. In this study, a heads pace gas chromatography mass spectrometry setup was developed to measure methanol in transformer oil. This setup consists of an auto sampler with a gas tight syringe, a gas chromatography unit with 60 m VF-624ms column and a quadrupole ion trap type mass spectrometer unit. Measurement of several laboratory-aged and service-aged oil samples were conducted with both external standard and internal standard calibration methods. Higher methanol values obtained from internal standard method confirmed that it is more suitable than external standard method.

27. REFERENCES A text book of environmental chemistry by “BALRAM PANI” “https://en.wikipedia.org/wiki/Gas_chromatography%E2%80%93mass_spectrometry https://en.wikipedia.org/wiki/Gas_chromatography https://www.youtube.com/watch?v=p3_WtEYIhTo https://www.youtube.com/watch?v=gU2st5-T1Go

28. THANK YOU