TLC - Isolation of Caffeine March 6th, 2009 Sublimation and...

Info iconThis preview shows pages 1–11. Sign up to view the full content.

View Full Document Right Arrow Icon
Isolation of Caffeine March 6 th , 2009 Sublimation and TLC
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Purification: Condensed Phase to Vapor Phase Boiling-liquid to vapor Sublimation-solid to vapor Reducing pressure-reduces boiling/sublimation point
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
To Vacuum 50 mL Vacuum flask (scrape all product) HUGE AMOUNT OF TAPE! clamp Small test tube should be close to the bottom WITHOUT touching Fill test tube with ice water after starting vacuum
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Carefully wash material off “cold finger” Use the remaining solid in the round bottom for your crude sample It only takes a little bit of material for the TLC.
Background image of page 6
Chromatography “Color Writing” general, versatile method for separation of components in a mixture identification of "unknowns" by comparison with reference samples no restrictions on sample type - organic, inorganic, biological, or medical high sensitivity - detection of μ g amounts or less (10 -6 g) Types of Chromatographic Methods Essential Components 1. TLC - Thin Layer Chromatography 1. stationary phase 2. LC - Liquid Chromatography (Column) 2. mobile phase HPLC - High Performance Liquid Chrom. 3. sample mixture 3. GC - Gas Chromatography
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Chromatography Stationary Phase Mobile Phase What does it do? stays put! flows around SP What is it? fine solid with fluid (liquid or gas) (physical form) lots of surface How does it effect retains sample by moves sample along sample movement? surface interaction Analogous to… an obstacle course “motivating force” Specifically for thin layer (250 μ m) ethyl acetate TLC of silica gel (SiO 2 ) x
Background image of page 8
TLC plate O O O | | | - O - Si - O - Si - O - Si - O - H | | | O O O | | | - O - Si - O - Si - O - Si - O - H | | | O O O silica gel - silicon dioxide (SiO 2 ) x (a common, inexpensive stationary phase) bulk (SiO 2 ) x These exposed OH units give silica gel a relatively polar surface. surface 250 μ m silica gel layer impregnated with a fluorescent indicator, on a plastic backing TLC
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Four Stages in TLC 1. Sample Application Capillary used to spot solution of each sample.
Background image of page 10
Image of page 11
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 31

TLC - Isolation of Caffeine March 6th, 2009 Sublimation and...

This preview shows document pages 1 - 11. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online