1. 5.2 Notes Organic Analysis Pg. 119-136

2. Objectives List and describe the parts of a gas chromatography Explain the difference between thin- layer chromatography and gas chromatography

3. Three chromatographic processes are used 1. Gas 2. High-Performance Liquid Chromatography 3. Thin-layer chromatography

4. Gas Chromatography (GC) Separates mixtures on the basis of their distribution between a stationary liquid phase and a moving gas phase Widely used because of its ability to resolve a highly complex mixture into its components with a few minutes

5. GC continued Moving phase is a gas Called carrier gas Moves through a column of stainless steel or glass with the liquid contained within the capillary column Stationary phase is a thin film of liquid contained with the column Simplified scheme = Figure 5-5, pg. 128

6. GC Scheme Carrier gas is fed into the column at a constant rate Carrier gas = inert, generally nitrogen or helium Sample is injected as liquid into a heated injection port with a syringe Immediately vaporized and swept into the column by the carrier gas

7. GC Scheme cont. Column is heated to keep the sample in vapor form Components of the sample travel in the direction of the carrier gas Speed determined by their distribution between stationary and moving phases Components become separated as they emerge from the column

8. GC Scheme cont. As each component emerges from column, it enters a detector Detector uses a flame to ionize the emerging chemical Generating an electrical signal recorded onto a strip chart Signal is recorded onto a strip-chart recorder as a function of time

9. Chromatogram Written record a plot of the results over time with each peak representing a component of the mixture time is called retention time Advantage to GC Extremely sensitive Yields quantitative results

10. Pyrolysis solid materials are heated to high temperatures so they decompose into numerous gaseous products Gaseous product is entered into carrier gas stream and run through normal GC

11. 5.2 Notes continued

12. High-Performance Liquid Chromatography (HPLC) Moving phase liquid phase Unknown sample injected in the column and carried by the liquid phase Different components are retarded to different degrees depending on their interaction with the stationary phase Takes place at room temperature Used for organic explosives, heat sensitive drugs (LSD)

13. Thin Layer Chromatography (TLC) Solid stationary phase and moving liquid phase Glass plate covered with silica gel or aluminum oxide, which serves as the solid stationary phase Plate placed upright into a closed chamber that contains a selected liquid

14. TLC cont. Liquid rises up the plate in a moving phase Separation occurs at point when components with a greater affinity for moving will move up the plate faster

15. TLC cont. Most results are colorless, materials must be visualized Plates placed under UV light revealing materials that fluoresce Fluoresce = emit visible light when exposed to a light of shorter wavelength Distance travelled is known at R f value which means the distance traveled by the component divided by the distance traveled by the moving liquid phase

16. Electrophoresis Separates materials according to their migration rates on a stationary solid phase Related to thin-layer chromatography Electrical potential is placed across the stationary medium Medium = starch or agar gel coated onto a glass plate

17. Electrophoresis Used for complex biochemical mixtures Proteins Enzymes in blood DNA in dried blood Separated proteins stained for visible observation

20. In-Class Assignment/Homework 5.2 Reinforcement Questions