![Polarity & Intermolecular Attractive
Forces
• More polar compounds will be more attracted to silica gel than non-polar
compounds due to intermolecular attractive forces
- a dipole-dipole interaction.
• The more non-polar compounds will travel more easily and more quickly
through the stationary phase.
• The mobile phase helps carry the compounds through the stationary
phase.
•Separation of compounds in a mixture is possible because compounds
have different polarities. Non-polar compounds will elute first and polar
compounds will elute last.
Si
OH
O
O
O
Si
+
-
-
-
+
Silica gel, [SiO2]n
10](https://image.slidesharecdn.com/chromatography2-150225081031-conversion-gate02/85/Chromatography-techniques-10-320.jpg)
Chromatography techniques
- 1. STK1094 Analytical Chemistry I Dayang Norafizan binti Awang Che Faculty of Resource Science and Technology Universiti Malaysia Sarawak This OpenCourseWare@UNIMAS and its related course materials are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
- 2. LU 8: Analytical Separation Techniques Learning Objectives At the end of this lesson, students should be able to: • Define the chromatography term • Explain different types of chromatography • Explain the principles of chromatography
- 3. What is Chromatography? • Chromatography is a technique for separating mixtures into their components in order to analyze, identify, purify, and/or quantify the mixture or components. 3 Separate • Analyze • Identify • Purify • Quantify ComponentsMixture CHROMATOGRAPHIC SEPARATIONS
- 4. Uses of Chromatography • Chromatography is used by scientists to: • Analyze – examine a mixture, its components, and their relations to one another • Identify – determine the identity of a mixture or components based on known components • Purify – separate components in order to isolate one of interest for further study • Quantify – determine the amount of a mixture and/or the components present in the sample 4
- 5. Types of Chromatography • Liquid Chromatography separates liquid samples with a liquid solvent (mobile phase) and a column composed of solid beads (stationary phase). • Gas Chromatography separates vaporized samples with a carrier gas (mobile phase) and a column composed of a liquid or of solid beads (stationary phase). • Paper Chromatography separates dried liquid samples with a liquid solvent (mobile phase) and a paper strip (stationary phase). • Thin-Layer Chromatography separates dried liquid samples with a liquid solvent (mobile phase) and a glass plate covered with a thin layer of alumina or silica gel (stationary phase). 5
- 6. *Terms in Separation Techniques* • Stationary phase: a phase that is fixed in place either in a column or on a planar surface. • Mobile phase :a phase that moves over or through the stationary phase, carrying the analyte with it. • Eluent: a solvent used to carry the components of a mixture through stationary phase. 6
- 8. Chromatography • Greek word chroma – “color” and graphein – “to write”. • Separations method - differences in partitioning behavior (migration rates) between a flowing mobile phase and a stationary phase to separate the components in a mixture. • Column holds the stationary phase and the mobile phase carries the sample through it. 8
- 9. Chromatography Basics How it works: sample is loaded onto the polar stationary phase. Polar compounds will adsorb onto the stationary phase to a greater extent than non-polar compounds. The mobile phase (eluting phase) helps “push” or elute the compounds either down a column (for CC) or up a plate (for TLC). The main concept to consider in chromatography is polarity. 9
- 10. Polarity & Intermolecular Attractive Forces • More polar compounds will be more attracted to silica gel than non-polar compounds due to intermolecular attractive forces - a dipole-dipole interaction. • The more non-polar compounds will travel more easily and more quickly through the stationary phase. • The mobile phase helps carry the compounds through the stationary phase. •Separation of compounds in a mixture is possible because compounds have different polarities. Non-polar compounds will elute first and polar compounds will elute last. Si OH O O O Si + - - - + Silica gel, [SiO2]n 10
- 11. Components that are weakly retained by stationary phase will move through the system more rapidly 11
- 12. REFLECTION •What is chromatography? •What are the examples of chromatography? •What is the principle of chromatography?