Chromatography

Front 1

Non-polar compound spotted in silica gel (polar) will travel further than a polar compound because????

Back 1

1. Polar compound interacts with polar silica gel, therefore it cannot travel as far as the "free" non-polar compound.

Front 2

What is Rf used for and how do you calculate?

Back 2

1. Rf = used to identify compounds in TLC
2. Distance traveled by compound / Distance traveled by Solvent

Front 3

What is retention time and volume?

Back 3

1. Retention time: time required for compound to elute off column.
2. Retention Volume: volume of mobile phase required to elute off compound.

Front 4

Solvent used to spot the plate should be _____________, why?

Back 4

1. Volatile
2. To minimize solvent interactions during development

Front 5

Spotted plate is placed into beaker containing what?

Back 5

1. Mobile phase - level must be below plate
2. As mobile phase moves up plate, it will interact with sample and separate compounds.

Front 6

How does separation occur when plate is placed into mobile phase?

Back 6

1. Mobile phase gets absorbed by plate and starts to move up plate, interacting with the spotted areas and causing a different length depending on interactions.

Front 7

What is elution?

Back 7

1. gravity or solvent pump to move the mobile phase through the column.

Front 8

Procedure for Part 1: Separation of Analgesics by TLC

Back 8

1. Obtain an unknown
2. Gather 2 precut TLC plates
3. Spot two standard compounds and one unknown per plate
4. Develop the plates - mark line before drying (view under UV)
5. Use a pencil to outline spots and calculate Rf's for each spot.
6. Identify unknown

Front 9

What is TLC:

Back 9

Thin Layer Chromatography

Front 10

Procedure for Part 2: Separation of Colorless Compounds by TLC

Back 10

1. Choose correct solvent to develop mixture
2. Spot the 3 compound mixture in three places on a precut TLC plate equal distance.
3. Find the one with 3 distinct circles ring pattern - use that.
4. Obtain unknown
5. Pick up two precut TLC plates and spot two compounds and one unknown on each.
6. Develop and dry - don't forget to mark before drying
7. Calculate Rf for each spot

Front 11

Procedure for Part 3: Separation of Acetylated Ferrocenes by Column Chromatography

Back 11

1. Obtain prepacked column.
2. Dissolve 200 mg of ferrocene:acetylated ferrocenes in a minimum amount of methylene chloride and load column.
3. Use the syringe to force pet ether through the column.
4. When loaded, bring to solvent pump station for flash chromatography - uses pressure to move mobile phase.
5. Collect fractions by observing color changes as the different compounds elute through the column.
6. Collect 1st colored fraction in an E flask (flask 1) - stop collecting when solvent colorless
7. When first band eluted - change mobile phase to 80:20 pet ether: ethylacetate mixture.
8. Collect second fraction in E Flask 2.
9. Now elute with mixture 50:50 pet ether: ethylacetate mixture. Collect 3rd color fraction in E Flask 3.
10. Spot TLC plates with flasks 1, 2, 3
11. Develop plate with 80:20 pet ether; ethylacetate
12. Evaporate collected solutions on steam bath - dry and weigh - calculate % recovery!