The Separation and Identification of Metal Ions Using Paper Chromatography
September 21, 2011
Kylie Case, Emma McKee, Rebecca Smith
Purpose: In this lab, one attempted to separate and identify ions, and discover the identity of
his/her mystery ion.
Theory: The main concept utilized in this lab was the use of chromatography. Chromatography
is a lab technique used to separate mixtures. It consists of a stationary phase and a mobile phase.
In this case the stationary phase was the filter paper and the mobile phase was the liquid solvent.
The solvent moved through the filter paper, and the ions were carried by the solvent at different
rates. The filter paper was sprayed so that a color complex was able to be formed, which allowed
one to see how the ions moved. The Rf calculation is the distance traveled by the solute/ the
distance traveled by the solvent. Retention factors show the quantitative measure of specific
components/ chemicals and their properties in a mixture. Chromatography is used a lot in biochemical laboratories to tell what chemical compounds are present in complex mixtures such as
cigarette smoke or petroleum products. There are four main types of chromatography that are:
liquid, gas, thin layer and the one done in class, paper chromatography.
Procedure: Students will locate a piece of filter paper(19 cm), then mark each metal ion (2 cm
from the edge and on every 3cm pattern), as well as the unknown(twice), and use a clean
capillary tube to place approximately 3mm spot of each respective substance to its corresponding
location on the line. Now, curve paper into a cylinder, staple the edges, and cover with plastic
wrap for approximately 30 minutes. The student should then, after waiting for a half an hour,
draw a line along the newly created solvent line, then let dry. After the paper is dry, use tongs to
slightly spray with staining agent, and then rinse with water while still using the tongs. The
students should then record the distance in cm of the distance from the center of each newly
formed circle to where each respective ion was originally placed.
Data:
Substance
Distance
Ion
Moved(cm)
Distance
Solvent
Moved(cm)
Rf
Color After
Staining
Cu(NO3)2
1.11
Ni(NO3)2 Fe(NO3)2 Co(NO3)2 Unknown#22
1.05
1.70
1.21
1.09/0.79
Unknown#24
0.98
6.89
6.93
6.99
.161
.151
Orange/Brown Yellow
6.91
6.89
6.98
.246
Blue
.176
Purple
.156/.113
.104
Orange/Red/Purple Orange
Calculations:
Distance ion moved/ distance solvent moved
EX: 1.11/6.89=.161
Error Analysis:
With every lab comes errors that could have occurred. Though students were supposed to perfect
their dot making techniques, the dots created still could have produced some error. For example
the dots created could have been too big or too small for desired results, such as having different
locations for the distance the ion moved, which could drastically alter the Rf calculation.