Gc
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Gas chromatography (GC) is used to separate and analyze compounds that can be vaporized without decomposition. GC works by injecting a sample into a heated port, carrying it through a column containing a stationary phase using a carrier gas, and detecting the separated components as peaks using a detector. Key aspects of GC include the carrier gas, injection port, column type and temperature profile, oven, and detector. Together, these components allow volatile compounds in a sample to be separated based on how they interact with the stationary phase in the column and are then detected at characteristic retention times.
Gc
- 1. hassan-alnajem Gas chromatography (GC) By : Hassan ALNAJEM Alnajemhassan@gmail.com
- 2. Gas chromatography (GC) • Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition. hassan-alnajem
- 3. GC • We used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition. For example : we use to check additives hassan-alnajem
- 4. GC Process A gas chromatograph consists of a flowing mobile phase, an injection port, a separation column containing the stationary phase, a detector, and a data recording system A sample is introduce d into a heated injector, carried through a separating column by an carrier gas, and detected as a series of peaks on a recorder when components leave the column. Selection of injection port, column , detector, Temperature & pressure profiles play important role in analysis of sample by gas chromatography. hassan-alnajem
- 5. Carrier (Mobile phase) Gas Cylinder. hassan-alnajem Mobile phases are generally gases such as Helium, Hydrogen, or nitrogen. The mobile phase or carrier gas flows through the instrument from a pressurized cylinder. Carrier gas must by chemically inert with the components of analysis. Carrier gas from cylinder are passed to GC I nst from Molecular sieve & silica bed to avoid any moisture carryover. Gasses are stored in cylinders fitted with Pressure regulators to supply the gas to the instrument at the set pressure. The cylinders are mostly kept outside the Lab (Analysis area) for safety purposes and the gasses are passed to the gas chromatograph instrument through stainless steel tubing/conduits.
- 6. Carrier Gas pressure (flow) Regulator Flow rate of carrier gas is first controlled by a two stage regulator fitted on the gas cylinder. Flow control of carrier is also controlled by additional controls within the instrument The pressure / flow rate gas regulator consists essentially of two gauge displaying Cylinder pressure & discharge pressure. Discharge pressure /flow rate of carrier gas is controlled /set by pressure control knob. hassan-alnajem
- 7. Injection Port The sample injector is a very critical part of the chromatographic equipment and needs to be well designed and well maintained. The precision and accuracy of a GC analysis will only be as good as that provided by the sample injector The sample is injected by a hypodermic syringe, through a silicone rubber septum into the injecti on port. Sample injected, gets vaporized, & carriers gas coming in injection port carries vaporize d sample in to the column. Temperature of injection port is kept above the Boling point of all the components. hassan-alnajem
- 8. Oven Oven is used to heat the column at set temperatures . Oven also control the temperature of column as indicated by the micro processor of the Instrument by help of exhaust fan. hassan-alnajem Oven
- 9. Column ( Stationary phase) There are two types of columns in common use in GC, and they are the packed column and the o pen tubular column (capillary column). The sample is injected into the mobile phase stream just before the front of the column. The colu mn is designed to produce the separation of different components. Separation is achieved by pro per selection of the column (Type of column, column dimensions) & temperature profile of the column. hassan-alnajem
- 10. PACKED COLUMN Packed Columns These columns are fabricated from glass, stainless steel, copper, or other suitable tubes. Stainless steel is the most common tubing used with internal diameters from 1-4 mm. T he column is packed with finely divided particles (<100-300 mm diameter), which is co ated with stationary phase. glass tubes are also used for large-scale separations. hassan-alnajem
- 11. CAPILLARY COLUMN capillary columns are finding broad applications. These are mainly of two types: Wall Coated Open Tubular (WCOT) Internal wall of capillary is coated with a very fine film of liquid stationary phase. Surface Coated Open Tubular (SCOT) Capillary tube wall is lined with a thin layer of solid support on to which liquid phase is adsorbed. The separation efficiency of SCOT columns is more than WCOT columns because of increased surface area of the stationary phase coating. Fused Silica Open Tubular (FSOT) Walls of capillary fused silica tubes are strengthened by a polyimide coating. These are flexible and can be wound into coils. hassan-alnajem
- 13. Detector Components separated by column elutes to detector , where it is detected in dimension of space & time. There are many typ es of detector based on applications. Detector used in analysis of additives is Flame Ionization detector (FID). In FID, compo nents (in volatile form) gets ionized by Hydrogen & Air flame. Each component of the mixture reaches the detector at a diff erent time and produces a signal at a characteristic time called a retention time (Rt). hassan-alnajem Flame Ionization Detector
- 14. Type of Detector : hassan-alnajem
- 15. Control & Date recording hassan-alnajem Goniometers The detector response is sent to a computer system where the progress of the sample is mon itored on the computer monitor in graphical form that displays detector response as a function of run time & milli volts. Main function of Computer are data acquisition & proces sing. Temperature & Pressure controls are also set by computer controls.
- 16. hassan-alnajem Thank you By : Hassan ALNAJEM Alnajemhassan@gmail.com