![ Kc = Conc. Of component A in the stationary phase [A]s
Conc. of component A in the mobile phase [A]m
A
+
B
Direction of mobile phase flow
Inject
Time
Conc. Of solute in
mobile phase
Conc. Of solution in
stationary phase
B A
B A
B
A
B
A
B
Schematic Representation of the Chromatographic
Process](https://image.slidesharecdn.com/gaschromatography-240918134547-9b8f5537/75/gas-chromatography-Gas-Solid-chromatography-and-gas-Liquid-Chromatography-pptx-6-2048.jpg)
More Related Content
Similar to gas chromatography (Gas Solid chromatography and gas Liquid Chromatography.pptx
More from Vandana Devesh Sharma
gas chromatography (Gas Solid chromatography and gas Liquid Chromatography.pptx
- 1. Unit IV (1) Instrumentalmethod of analysis Gas Chromatography part-1 Mrs Vandana Sharma Assistant Professor
- 2. Introduction Theory Instrumentation Derivatization Temperature programming Advantages Disadvantages And Applications Contents
- 3. Explain theprinciple of GLC. Describe various types of of columns used in GC. 8 Explain the instrumentation in Gas chromatography in detail. Discuss the application of GC in drug analysis. 10+6 Different types of detectors used in GC. 8 Discuss the principle, instrumentation and various applications of gas chromatography. 16 Explain Van Deemter equation. Describe in detail the instrumentation of gas chromatography. 16 Write the theory of chromatography and describe the instrumentation of GAS chromatography. 8 Detectors used in Gas Chromatography. 4 Derivatization of GC 2 Give a detailed account on Gas Chromatography. 5 Previous years questions
- 4. In gaschromatography Mobile phase -gas and stationary phase -solid and liquid Gas solid chromatography GSC)- When the stationary phase is solid Gas Liquid Chromatography (GLC)- When the stationary phase is liquid In gas chromatography, a moving gas phase passed over a stationary sorbent to separate the mixture of components. Note-This technique is similar to that of liquid- liquid chromatography, with only the exception that in the – 1.gas chromatography- mobile phase -a moving gas is used While 2.in liquid-liquid chromatography- mobile phase -a liquid. The stationary phase remains same, i.e. a solid or a liquid Gas Chromatography
- 5. Gas Chromatographyor Gas Liquid Chromatography is a technique applied for separation, identification and quantification of components of a mixture of organic compounds by selective partitioning between the stationary phase and mobile phase inside a column followed by sequential elution of separated components. The technique is suitable for separation of compounds having following characteristics : High volatility Thermal stability Low molecular weights Principle The substance to be analyzed is partitioned b/w mobile and stationary phases. During the separation, the sample is vaporized and carried through the column by mobile phase (i.e. the carrier gas) The different components get separated based on their vapour pressure and affinities for the stationary phase. The affinity of component towards the stationary phase is termed as distribution constant (Kc) or partition coefficient.
- 6. Kc =Conc. Of component A in the stationary phase [A]s Conc. of component A in the mobile phase [A]m A + B Direction of mobile phase flow Inject Time Conc. Of solute in mobile phase Conc. Of solution in stationary phase B A B A B A B A B Schematic Representation of the Chromatographic Process
- 7. GC modes showinginteraction between the mobile phase and the stationary phases.
- 8. Advantages andDisadvantages of Gas Chromatography Chromatography has evolved, from paper chromatography to TLC and chromatography to instrumental techniques including GC and HPLC. Gas chromatography (GC) is the significant analytical method for the separation of volatile compounds in a mixture by injecting a liquid or gaseous sample into a mobile phase, usually called the carrier gas, and passing the gas through a stationary phase. The mobile phase consists of an inert gas it may be nitrogen, helium, or argon and the column can be packed or capillary they can available in different diameters and lengths as per the requirement of the sample. This kind of chromatography isolates analytes based on the volatility of analytes. The more volatile compound will be separated rapidly, whereas the less volatile compound will gradually be eluted from the column. The gas chromatography follows the principle of the partitioning of volatile compounds with mobile phase and stationary phase. Several detector options are available with high sensitivity, to detect a wide range of samples that is not possible with other chromatographic techniques. The different types of GC detectors are flame ionization (FID), thermal conductivity, nitrogen phosphorous, photo-ionization, electron capture, flame photometric, electrolytic conductivity detector, and mass spectrometer, etc.
- 9. Advantages of gaschromatography (GC): The major advantage of gas chromatography is its high sensitivity, resolution, and separation ability, which allows it to separate a wide range of volatile compounds. It can be upgraded to a mass spectrometer (MS), which is used to determine the mass-to-charge ratio of ions. It comes with a variety of detectors and injectors that can be used for various pharmaceuticals as well as other applications. Gas chromatography can analyze a sample much faster than other chromatographic techniques. It is a robust method of separation that gives the superior signal-to-noise ratio. It only takes a very small amount of sample to inject, and its detectors are extremely sensitive, allowing it to detect extremely low concentrations (ng-pg). As per the requirement of the molecule, there are different types of GC columns are available in many diameters and lengths. Gas chromatography is easy, automated, and has quick analysis of data which gives comparatively high precision, accuracy, and reproducible results. Operational parameters such as flow rate, temperature, and pressure, etc. are easy to change even during chromatographic runs.
- 10. Disadvantages of agas chromatography (GC) The major disadvantage of GC is that only volatile and thermally stable compounds can be separated using gas chromatography. Detectors which are used in the GC are destructive, except for MS. Selectivity in HPLC or TLC is also better as a mobile phase can be easily changed. In GC, you can just modify the temperature of the column and oven, but you cannot change the mobile phase as it has a constant flow of carrier gas (helium, nitrogen). Since hydrogen gas, which is used for flame, is highly flammable, care must be taken when using it. It is impossible to recover individual sample components.
- 11. The followingcomponents make up the instrumentation of chromatogaphy 1. carrier gas maintain at high pressure and delivered at rapid and reproducible rate 2. sample injector 3. Separation column 4. Detector 5. Thermostated chambers for regulating the temprature of column and deterctors 6. Aplifier and recorder Instrumentation
- 15. Separation ingas chromatography carried out in tubular column ( Glass, metal, or teflon) filled with adsorbent (the stationary phase). Adsorbent- is packed as fine size graded powder or while - the liquid before being packed in column are either 1. coated as a fine film on column wall or 2. are coated over an inert size graded porous support (such as fire brick powder) A carrier gas ( the mobile phase) is continuously made to flow through the column so that the sample components are distributed in the column. The sample vapour is introduced in the column through the carrier gas entrance end. Different sample components adsorbed on the stationary phase to different extents, and this depends on their distribution coefficients. The carrier gas immediately sweeps further the portion of each component in the gas phase. Thus, a fraction of adsorbed amount desorbs out to maintain the value of distribution coefficient.
- 16. Simultaneously, outof the amount swept away, some amount again goes into the adsorbent at the next point in the column to maintain the distributed coefficient value. This process continues and the band for each component moves further in the column. 1. Carrier gas- Most widely used- Hydrogen, helium, nitrogen and air Hydrogen- Fuel gas – They support the flame in Flame ionization detector (FID) detector but-dangerous to use Helium- Next best gas due its good thermal conductivity, inertness, low density, and greater flow rate. But it is expensive. Nitrogen- Inexpensive but reduces sensitivity Air- Zero air – These are the purified air that plays the role of oxidant to support the combustion of flame in the detector use When atmospheric oxygen is useful to the detector or separation
- 17. Selection of carriergas Should be inert ( not react with sample , stationary phase or contacted hardware. Should be suitable for detector and sample to be analyzed Should be available in high purity should give best column performance Should not be expensive Should not cause any fire or explosion hazard. 2.Stationary phase in gas chromatography Gas liquid chromatography can be available in almost an infinite variety of liquid partition materials. The liquid or stationary phase in gas chromatography can be divided into nonpolar, intermediate polarity, polar carbowaxes, and hydrogen bonding compounds like glycol. The maximum temperature of the stationary phase can be determined by its volatility. The excess volatility of the stationary phase can shorten the life of the column. Loading of the column by stationary phase can be expressed by percentage of weight. For example, 15% means, a 100 g column has 15 g of stationary phase.
- 18. Stationary phasein gas chromatography 3. Sample injector- Used for introducing sample in reproducible manner and should vaporize it rapidly so that the sample enters the column as a single slug. The injector is a heated block where the sample is injected. Through the carrier gas stream, the sample is spontaneously vaporized and led to the column. With the help of a gas-tight syringe, the liquid sample mixtures are injected. The temperature should not be very high to avoid sample decomposition. Type Stationary phase GLC Squalene, silicon oil, nonpolar polyethylene, glycol, glass Teflon beads, etc. GSC (usual) Silica gel, alumina, charcoal, molecular sieve inorganic salts, mineral, porous polymers. GSC (reverse-phase) Silica alumina coated with organic or inorganic compounds or complexes.
- 19. Solid samplesare either dissolved in volatile liquids prior to their introduction or are directly introduced if they are liquefiable. Gas sample is introduced into the carrier gas stream using a special gas sampling valves.
- 20. 4. Gas chromatographycolumn The gas chromatography column can be made by tubing coiled into an open spiral. Made of glass or metal tubing. used copper or stainless steel for high-temperature operation. The velocity of the carrier gas flow rate depends on the inner diameter of the chromatographic column. The usual size of the column is 2 meters. Types 1. Packed columns 2. Open tubular or capillary or Golay columns 3. Support coated Open tubular columns 4. Wall coated open tubular columns 5. Porous-Layer Open- Tubular Columns 6. Support-Coated Open-Tubular Columns
- 21. Component of aColumn – Oven The column is enclosed by a column oven which is responsible for maintaining a constant temperature during isothermal operation. This temperature when temperature programming is needed can be increased in a controlled way for acquiring effective separation of mixture components possessing different volatilities.
- 22. 5. Detector Thedetector can detect the arrival of components coming from the column to provide an electrical signal. Type of detectors- Pressure detector and temperature detector – TDS, FID are the two major groups of detectors used in gas chromatography. The detector in gas chromatography instrumentation is situated near the column to avoid the condensation of liquids or detect the sample before decomposition. In a packed column gas chromatography instrumentation, we used mostly a thermal conductivity detector (TCD) or a flame ionization detector (FID). Among these TCD is the most popular. A flame ionization detector (FID) is most useful where the effluent is suitably attenuated by a stream splitter. TCD detector contains four heat sensing elements made by thermistors or resistance wires. The thermometers are electronic semiconductors of fused metal oxides whose electrical resistance varies with temperature.
- 23. The detectors-Brain centre of the instrument Good detector characteristics 1. Stable against the effects of extraneous noise in detector system 2. Reproducibility and sensitivity to a wide range of solute vapours 3. Detector sense and measure the small amount of separated components present in the carrier gas stream leaving the column 4. Output from the detector is feed to the recorder, which produces a pen-trace (Chromatogram) Factors affect the choice of detector 1. Concentration level to be measured 2. The nature of separated components eg. If concentration level (Components) in microgram then thermal conductivity detector is used Concentration range of separated components is less than microgram means (picogram level) then flame ionization detector or electron capture detector (more sensitive detectors)
- 24. Principle of TDS-is based on the measurement of difference in thermal conductivity between carrier gas and the carrier gas containing sample vapour mixture TDS- a heated mental filament to sense the changes in thermal conductivity of the carrier gas stream TDS- helium (preferred due to safety ground) and hydrogen TDS- 2 pairs of matched filaments (arranged in – wheat stone circuit) TDS/Thermal conductivity detector/ Katharometer/ Thermal conductivity cell/ Hot wire detector Most widely used detectors Thermal conductivity detector Flame ionization detector Electron capture detector
- 25. 1. reference channel 2.sample channel 1. In reference channel -One pair of filaments- Surrounded by the pure carrier gas 2. In sample channel- Other pair of filaments- Surrounded by effluent from GLC column TDS – two channels Pure carrier gas
- 27. When pure gaspass over both the pair if thermistors the bridge is balanced Working of TDS When vapor emerges from the column The rate of cooling of sample filaments changes and bridge become unbalance The degree of this imbalance is measure of concentration of vapor in carrier gas The signal from the detector to produce chromatogram
- 28.
- 29. Effluent from columnis mixed in hydrogen gas Burned in air to produce a flame Which has a sufficent energy to ionize the solute molecules having low ionization potentials The ions produces are collected at electrodes And resulting ion current is measured Note- in FID A wire extending to the tip of flame act as positive electrode (Anode) Burner jet act as negative electrode (Cathode) Working of Flame ionization detector
- 30. Electron capture detectorECD A beam of electrons is produced by beta emitter Radioactive foil 65 Ni or 3 H When the carrier gas passes over the emitter, the carrier gas ionizes and producing electrons In absence of the compound, ionization of carrier gas produces a constant standing current When solute is eluted out from the column, it captures electron towards it Hence current decreases This decrease gives idea about the concentration of solution in the sample Radioactive foil 65 Ni or 3 H
- 31. Note- ECD-responds to compounds whose molecules have electron affinity. Eg. Chlorinated compounds, Alkyl lead etc ECD- using a metal foil coated with a tritium containing compounds as a steady source of slow electrons Electron capture detectors (ECD) are typically used in environmental testing for detecting PCB's, organochlorine pesticides, herbicides and various halogenated hydrocarbons. With an electron capture detector, a beta emitter such as radioactive tritium or 63 Ni is used to ionize the carrier gas. • Other detectors are • Thermionic emission detector, Flame photometric detector, photo ionization detector, electrolytic conductivity detector
- 32. 6. Data system It is a set of dedicated software that provides control over many important operational parameters like injection sequence, wash cycles, over-temperature control, the flow rate of gases, detector wavelength, etc. Simultaneously, the data station calculates and displays the parameters. Gas chromatographic analysis The X-axis – Retention time of peak (Rt) This is calculated from the time the sample was injected into the column (t0) till it reaches the detector. Every analyte peak has a retention time that is measured from the apex of the peak, just like tR. The Y-axis – Detector response This shows the measured response of the analyte peak within the detector.
- 33. The baselinehere represents the signal received from the detector where no analyte is eluting from the column or is beneath the detection limit. in situations where the baseline is found higher than usual-- It is considered as an indication of a problem or indication to check the maintenance, Measurements such as width at the baseline, width at half height, area, and total height can be withdrawn from the peak. For better sensitivity and better resolution, narrower, sharper peaks are desired. The accuracy of measurements is influenced by the total number of data points present across a peak.
- 34. FIGURE: Chromatogram outputfrom GC.
- 35. Types Majorly,there are two gas chromatography types into which it is classified – GLC or gas-liquid chromatography and GSC or gas-solid chromatography. Both the methods use either liquid or solid as a stationary phase while using gas as the mobile phase. In Gas-solid chromatography, the retention of analytes is due to physical adsorption. On the other hand, gas-liquid chromatography separates the ions or molecules that are dissolved in a solvent. The underlying principle is – as the sample solution makes contact with the second solid or liquid phase, the solutes will start interacting with the other phases. Due to different adsorption rates, ion-exchanges, partitioning or sizes, the interaction will vary, and that’s what will enable the separation of the mixed components from each other. These differences will make the sample mixture pass at different rates through the column, and the compounds can be separated.
- 36. A GasChromatograph like any other analytical instrument has evolved from one with several knobs and dials to one having a simple microprocessor-based keypad to control the operational parameters. The simplification has resulted in ease of operation and time-saving. An understanding of the main component parts will help in maximum utilization of system capabilities.
- 37. Stationary Phase A solid phasewhich absorbs the sample components and later releases them in a sequential manner Mobile Phase A stream of carrier gas used for transporting sample from injection port to the column to the detector Column Oven A compartment inside which the column is mounted. It maintains a constant temperature or a varying temperature in response to a set temperature programme. Detector A device which gives the signal response in terms of area counts under a peak Column Efficiency Expressed in terms of HETP expresses the resolving power of the GC column Packed Column A steel or glass tube wound as a coil which holds the stationary phase Autosampler A device capable of holding several samples, standard vials and automatically injects a predetermined sample volume into the gas chromatograph Injector Manual or automated device for precise sample volume introduction Exam purpose Important definition and full forms
- 38. FID Flame Ionisationdetector which responds to most organic compounds TCD Thermal Conductivity detector. Universal and nondestructive detector
- 39.