Introduction Chromatography is a widely used method of separating mixtures into their component parts Paper chromatography separates substances using two things called phases The first thing is chromatography paper also called the ID: 496942
Download Presentation The PPT/PDF document "Paper Chromatography" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Paper ChromatographySlide2
Introduction
Chromatography is a widely used method of separating mixtures into their component parts
.
Paper chromatography separates substances using two things (called phases)
The first thing is chromatography paper; also called the
stationary phase
Next we have a solvent – called the
mobile phaseSlide3
Basic Principles
When the paper comes in contact with the solvent, the solvent moves up the paper
The solvent that is used depends
upon the substances you are
trying to separate. Commonly used solvents include water, alcohol (ethanol or isopropanol) and acetone.Slide4
Separation
the different components of a mixture will travel different lengths along a piece of paper when a solvent is allowed to travel up
it
The length that a specific component will travel along the paper is dependent upon several forces. Slide5
Propelling Forces and Retarding Forces
Propelling Forces
The main propelling force is the flow of the solvent
the rate that a substance will flow in that solvent is dependent on its
solubility
More soluble
Less soluble
Retarding Forces
The main retarding force is the degree to which the substance adheres (sticks) to the paper
A substance with a strong adherence will not travel as far as a substance with low adherenceSlide6
Solubility
If a component of a mixture is completely soluble in a solvent then it will travel farther along the paper than a component that is not soluble or only partially soluble
.
The degree to which a substance is soluble depends on the solvent
Generally speaking, a polar substance will have a greater solubility in a polar solvent (like dissolves like) and non polar substances will be more soluble in a non-polar solventSlide7
R
f
Values
To quantify the degree to which a substance is moved by a solvent,
Rf values are usedRf stands for “Retardation Factor“(sometimes called “rate of flow”)Is a simple calculation:
R
f
=
distance substance moved
distance of lead front of solventSlide8
R
f
Value Calculation
Here the
R
f values of two substances in a mixture are calculated