the safety materials and wear goggles when working
Question # 00121549
Posted By:
Updated on: 10/22/2015 02:57 AM Due on: 11/21/2015
Chromatography of Food Dyes
Peter Jeschofnig, Ph.D. Version 42-0148-00-01
Review the safety materials and wear goggles when working
with chemicals. Read the entire exercise before you begin. Take
time to organize the materials you will need and set aside a
safe
experiment summary:
Students will have the opportunity to learn how mixtures of
compounds can be separated and determine what food dyes
are found in certain foods by using paper chromatography.
They will learn how solubility is affected by polarity.
148
© Hands-On Labs, Inc.
Experiment
ObjEctivEs
•
●
To learn how mixtures of compounds can be separated
•
●
To learn what food dyes are found in certain foods
Chromatography of food dyes
www.LabPaq.com
149
©Hands-On Labs, Inc.
Experiment
matErials
Chromatography of food dyes
materials From:
Student Provides
label or box/ baG:
Qty
item DesCriPtion
1 1 1 1 Distilled water Sa
1 1 1 16
PencilTapeToothp
11
strawberry Kool-A
11
Set of food colorin
red, yellow, green
Small bag of M&M
From LabPaq
111
Beaker, 50 mL, pl
24
FDC Blue Dye #Experiment Bag
Chromatography of
Food Dyes
Special Papers Bag
Special Papers BagCK-2
1
1111
11
FDC Blue Dye #- 0.5 mL in Vial F
FDC Yellow Dye
Dye #-6 - 0.5 mL
3
Filter Paper Chrom
note: The packaging and/or materials in this LabPaq may differ
slightly from that which is listed above. For an exact listing of
materials, refer to the Contents List form included in the LabPaq.
www.LabPaq.com
150
©Hands-On Labs, Inc.
Experiment
Chromatography of food dyes
DiscussiOn anD rEviEw
Chromatography is a technique commonly used to separate
mixtures of compounds into their constituent components.
Separation is based on a physical characteristic of the compounds,
such as size or polarity.
Paper chromatography is a simple yet extremely effective method
for determining the presence of a substance in a mixture or for
separating components from a mixture. A strip of paper (special
chromatography paper or simple filter paper) serves as the
stationary phase. A small spot of the sample mixture to be
separated is placed near one end of the paper strip and a solvent (or
solvent mixture) called the mobile phase (or eluent) is passed over
the spot. The solvent moves up the plate due to capillary action the same way that water will move up a paper towel - and carries
with it the various components in the spot. This column is called
the solvent-front.
The sample is carried along by the solvent and moves upward to
the extent that it dissolves in the solvent more than it adheres to the
adsorbent. Every substance has a slightly different solubility in a
given solvent and will adhere to a solid adsorbent in a different
degree. Thus, the different components of a mixture will be carried
along by the solvent at different rates and consequently will be
separated. Differences in solubility and degree of adsorption are
due to the different sizes and shapes of molecules as well as to
differences in polarity.
If two compounds are started at the same place on a stationary
phase and a solvent is passed over them (elution) one compound
will move along the paper strip faster than the other. After a period
of time the flow of the mobile phase is stopped and the strip is
dried. If the components of the mixture are colored the separated
compounds can be observed directly. If they are colorless another
method (usually chemical) must be used to show their presence.
Paper chromatography tells whether or not a sample is pure, and if
it is not, how many different components are present. The ending
positions of each spot can be compared with those from known
compounds (standards) to ascertain the presence or absence of a
component. The location of the compound is indicated by an “Rf”
value. For a given substance the distance it moves depends upon
the total time of the experiment and upon the physical and
chemical properties of the system. However, the distance the
compound moves relative to the distance the solvent (or mobile
phase or eluent) moves is a characteristic of that compound.
Thus, Rf value = compound distance solvent distance
The choice of a solvent in paper chromatography is crucial. The
solvent must dissolve the various components in the mixture and
there must be at least slight differences in solubility of each
component. If the components are insoluble they will remain
where originally placed and not move with the solvent. If all the
components are extremely soluble then each component of the
mixture will travel along with the leading edge of the solvent and
not separate. Usually one pure solvent will not provide separation
or give resolution. Then a mixture of solvents must be found to
analyze the components.
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151
©Hands-On Labs, Inc.
Experiment
Chromatography of food dyes
prOcEDurE
Completely read all instructions and assemble all equipment and
supplies before beginning work on this experiment.
Before beginning, set up data tables similar to the ones shown in
the Lab Report Assistant section.
In this exercise we will separate food dyes from a variety of
sources. The separation is based on polarity. Most dyes are all
polar and will be soluble in water. We will absorb the dyes on
paper, which is also polar. Then we will use slightly salted water as
our solvent to move the dyes on the paper. Since some of the dyes
are more polar than others, they are absorbed more tightly to the
paper and are moved more slowly by the salt water.
FD&C dyes refer to specific dyes approved for human
consumption under the US government’s Food, Drugs, and
Cosmetics Act. Food coloring typically found in grocery stores
may vary from brand to brand. One brand of food coloring - like
the colors used for different food products - may consist of only
one FD&C dye, while another brand may be a mixture of two of
more dyes. This experiment will show you the various color
constituents of Kool-Aid®, your grocery store’s brand of food
coloring, plus the other food items you select to test.
1.
Using the 50-mL beaker, dissolve a pinch of salt into 50 mL of
warm (room temperature) distilled water. Stir until completely
dissolved and set aside.
2.
Obtain two sheets of Filter Paper Sheets Chromatography – 14 x
7cm from your LabPaq.
a.
Draw a thin horizontal line with a pencil (NOT a pen!) across the
paper 10 mm (1 cm) from the bottom. The line should just barely
be visible.
b.
With a pencil, draw nine (9) small cross lines along the horizontal
line 1.5 cm apart, as shown. Figure 1: Example of the filter paper
sheets
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152
©Hands-On Labs, Inc.
Experiment
Chromatography of food dyes
3.
On Sheet 1, from left to right, lightly label in pencil each
section between the cross lines with the abbreviation for the six
FD&C food colors from your experiment bag that will be
tested, i.e., B1, B2, R3, R40, Y5, and Y6.
4.
Also on Sheet 1, but now right to left, place the labels KG and KS
to represent the Kool-Aid® Grape and Kool-Aid®Strawberry
drink mixes to be tested.
5.
On Sheet 2 from left to right, lightly label in pencil each section
between the cross lines with the abbreviation for the grocery store
food colorings that will be tested, i.e., R, Y, G, and B.
6.
Also on Sheet 2, but now from right to left, place the label UK for
unknown and then M plus a letter for the color of four different
candies from your bag of M&Ms®, i.e., MR, MY, MB, etc.
7.
Set Sheet 2 aside and perform the following for Sheet 1. After you
have completed the experiment for Sheet 1, repeat for Sheet 2.
8.
For each dye on the sheet to be tested:
a.
First place a few drops in a well of the 24-well plate.
b.
Next, dip a clean toothpick tip into the dye and then briefly touch
the toothpick tip to the CENTER of the appropriately marked
section on the horizontal line on the filter paper.
c.
note 1: A small drop of water on a little bit of Kool-Aid®
powder will be sufficient to make a sample to spot the paper. A
small drop of water on the coating of an M&M® will dissolve
enough dye for the toothpick to pick up. The coating of blue
and brown M&Ms® is made up of very interesting dye
combinations!
d.
note 2: Apply only a small drop of each dye on the paper. Big
drops may spread over a greater area and overlap with other
dyes. This is called band broadening. Although a larger dot will
produce a more vivid color, a smaller dot will show the most
distinct break between colors.
Once the paper is spotted with all the dyes, allow the spots to dry
for a few minutes.
Figure 2: Procedure to form the paper into a cylinder
9. Now form the paper into a cylinder with the edges touching, but
NOT overlapped, and staple at the top and bottom as shown. (You
may want to use small pieces of tape on the outside to lightly hold
the cylinder together while you securely staple it. If so, remove the
tape after stapling.) Set the cylinder aside for a moment.
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153
©Hands-On Labs, Inc.
Experiment
Chromatography of food dyes
10.
The salt water (~0.1% NaCl) you previously prepared will be your
eluting solvent and a petri dish will be your elution chamber. Pour
salt water into the clean and empty petri dish to a depth of about
1/2 cm. This is just enough to cover the bottom of the elution
chamber.
11.
Set your cylinder next to the petri dish with the spots at the bottom
and look to make sure the solvent level is below the line of dye
spots. If it is not pour out a little solvent until it is. The spots at the
bottom of the chamber must be above the solvent level for this
experiment to work well.
12.
Carefully drop the dye cylinder into the eluting chamber, making
sure not to touch the petri dish sides. The solvent-front will travel
up the paper rapidly at first and then will slow down. Let the
solvent-front rise for a few minutes, but immediately remove the
cylinder if any column moves up higher than 2 cm from the top of
the paper. If all the solvent is soaked up before the front has time to
move toward the top of the paper carefully add a little more solvent
to the petri dish.
13.
When complete remove the cylinder from the chamber and
immediately mark the top of each solvent-front with a pencil.
Allow the paper to dry for several minutes.
14.
Then measure to the nearest millimeter and record the heights of
the dye and solvent-front in each column:
a.
Start from the original horizontal pencil line and measure to the top
center of where the dye stops in each column on the paper. Record.
b.
Measure the heights of the solvent-front for each column from the
original horizontal pencil line to the lines drawn in Step 14.
Record.
15.
Calculate and record the Rf value for each spot: Rf = dye
distance/solvent distance
16.
Repeat Steps 8 through 15 for the items listed on Sheet 2.
17.
By comparing the color columns of the unknown sample and the
food items with those of the FD&C food dyes it is possible to
determine which dyes are used in the Kool-Aid®, in the grocery
food colorings, and in the M&Ms®. Identify the following:
a.
The FD&C color(s) making up the unknown,
b.
The FD&C color(s) making up the grocery store food colorings.
Don’t forget to indicate the brand name; e.g., Kroger®,
McCormick®, etc., and
c.
The FD&C color(s) making up the Kool-Aid® drinks and
M&M’s®.
www.LabPaq.com
154
©Hands-On Labs, Inc.
Experiment
Chromatography of food dyes
Chromatography of Food Dyes
Peter Jeschofnig, Ph.D. Version 42-0148-00-01
lab rEpOrt assistant
This document is not meant to be a substitute for a formal
laboratory report. The Lab Report Assistant is simply a summary
of the experiment’s questions, diagrams if needed, and data tables
that should be addressed in a formal lab report. The intent is to
facilitate students’ writing of lab reports by providing this
information in an editable file which can be sent to an instructor.
ObsErvatiOns
Enter data tables, observation questions from the procedures and
descriptions of diagrams to be drawn or pictures to be included
here, one per text box.
Data
Table
Sheet
1:
FD&C
Food
Colors
Color
blue1
blue2
red3
red40
yellow5 yellow6 Solvent
Distanc
e (mm)
rf
Data Table Sheet
1: Drink Mixes
Kool-Aid®
Grape
substance
Kool-Aid®
Strawberry
Solvent
Distance (mm)
Distance (mm)
rf
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155
©Hands-On Labs, Inc.
Experiment
Chromatography of food dyes
Data Table
Sheet 2:
Store Food
Colors
substance
store red
store
yellow
store
Green
store
blue
Solvent
Distance
(mm)
rf
Data Table
Sheet 2:
Candy
Colors
substance
M&M
Green
M&M
Yellow
M&M
Blue
M&M
Red
Distance
(mm)
rf
www.LabPaq.com
156
©Hands-On Labs, Inc.
Experiment
Chromatography of food dyes
QuEstiOns
A. Why can’t a pen be used to draw the baseline on the
chromatography paper?
B. Why is it important to stop the chromatograph before the
solvent reaches the top of the paper?
Solvent
C. Why is it important to keep the dye spots above the solvent
level?
D. Why is it important to mark the solvent level on the
chromatography paper when you remove it from the petri dish?
Peter Jeschofnig, Ph.D. Version 42-0148-00-01
Review the safety materials and wear goggles when working
with chemicals. Read the entire exercise before you begin. Take
time to organize the materials you will need and set aside a
safe
experiment summary:
Students will have the opportunity to learn how mixtures of
compounds can be separated and determine what food dyes
are found in certain foods by using paper chromatography.
They will learn how solubility is affected by polarity.
148
© Hands-On Labs, Inc.
Experiment
ObjEctivEs
•
●
To learn how mixtures of compounds can be separated
•
●
To learn what food dyes are found in certain foods
Chromatography of food dyes
www.LabPaq.com
149
©Hands-On Labs, Inc.
Experiment
matErials
Chromatography of food dyes
materials From:
Student Provides
label or box/ baG:
Qty
item DesCriPtion
1 1 1 1 Distilled water Sa
1 1 1 16
PencilTapeToothp
11
strawberry Kool-A
11
Set of food colorin
red, yellow, green
Small bag of M&M
From LabPaq
111
Beaker, 50 mL, pl
24
FDC Blue Dye #Experiment Bag
Chromatography of
Food Dyes
Special Papers Bag
Special Papers BagCK-2
1
1111
11
FDC Blue Dye #- 0.5 mL in Vial F
FDC Yellow Dye
Dye #-6 - 0.5 mL
3
Filter Paper Chrom
note: The packaging and/or materials in this LabPaq may differ
slightly from that which is listed above. For an exact listing of
materials, refer to the Contents List form included in the LabPaq.
www.LabPaq.com
150
©Hands-On Labs, Inc.
Experiment
Chromatography of food dyes
DiscussiOn anD rEviEw
Chromatography is a technique commonly used to separate
mixtures of compounds into their constituent components.
Separation is based on a physical characteristic of the compounds,
such as size or polarity.
Paper chromatography is a simple yet extremely effective method
for determining the presence of a substance in a mixture or for
separating components from a mixture. A strip of paper (special
chromatography paper or simple filter paper) serves as the
stationary phase. A small spot of the sample mixture to be
separated is placed near one end of the paper strip and a solvent (or
solvent mixture) called the mobile phase (or eluent) is passed over
the spot. The solvent moves up the plate due to capillary action the same way that water will move up a paper towel - and carries
with it the various components in the spot. This column is called
the solvent-front.
The sample is carried along by the solvent and moves upward to
the extent that it dissolves in the solvent more than it adheres to the
adsorbent. Every substance has a slightly different solubility in a
given solvent and will adhere to a solid adsorbent in a different
degree. Thus, the different components of a mixture will be carried
along by the solvent at different rates and consequently will be
separated. Differences in solubility and degree of adsorption are
due to the different sizes and shapes of molecules as well as to
differences in polarity.
If two compounds are started at the same place on a stationary
phase and a solvent is passed over them (elution) one compound
will move along the paper strip faster than the other. After a period
of time the flow of the mobile phase is stopped and the strip is
dried. If the components of the mixture are colored the separated
compounds can be observed directly. If they are colorless another
method (usually chemical) must be used to show their presence.
Paper chromatography tells whether or not a sample is pure, and if
it is not, how many different components are present. The ending
positions of each spot can be compared with those from known
compounds (standards) to ascertain the presence or absence of a
component. The location of the compound is indicated by an “Rf”
value. For a given substance the distance it moves depends upon
the total time of the experiment and upon the physical and
chemical properties of the system. However, the distance the
compound moves relative to the distance the solvent (or mobile
phase or eluent) moves is a characteristic of that compound.
Thus, Rf value = compound distance solvent distance
The choice of a solvent in paper chromatography is crucial. The
solvent must dissolve the various components in the mixture and
there must be at least slight differences in solubility of each
component. If the components are insoluble they will remain
where originally placed and not move with the solvent. If all the
components are extremely soluble then each component of the
mixture will travel along with the leading edge of the solvent and
not separate. Usually one pure solvent will not provide separation
or give resolution. Then a mixture of solvents must be found to
analyze the components.
www.LabPaq.com
151
©Hands-On Labs, Inc.
Experiment
Chromatography of food dyes
prOcEDurE
Completely read all instructions and assemble all equipment and
supplies before beginning work on this experiment.
Before beginning, set up data tables similar to the ones shown in
the Lab Report Assistant section.
In this exercise we will separate food dyes from a variety of
sources. The separation is based on polarity. Most dyes are all
polar and will be soluble in water. We will absorb the dyes on
paper, which is also polar. Then we will use slightly salted water as
our solvent to move the dyes on the paper. Since some of the dyes
are more polar than others, they are absorbed more tightly to the
paper and are moved more slowly by the salt water.
FD&C dyes refer to specific dyes approved for human
consumption under the US government’s Food, Drugs, and
Cosmetics Act. Food coloring typically found in grocery stores
may vary from brand to brand. One brand of food coloring - like
the colors used for different food products - may consist of only
one FD&C dye, while another brand may be a mixture of two of
more dyes. This experiment will show you the various color
constituents of Kool-Aid®, your grocery store’s brand of food
coloring, plus the other food items you select to test.
1.
Using the 50-mL beaker, dissolve a pinch of salt into 50 mL of
warm (room temperature) distilled water. Stir until completely
dissolved and set aside.
2.
Obtain two sheets of Filter Paper Sheets Chromatography – 14 x
7cm from your LabPaq.
a.
Draw a thin horizontal line with a pencil (NOT a pen!) across the
paper 10 mm (1 cm) from the bottom. The line should just barely
be visible.
b.
With a pencil, draw nine (9) small cross lines along the horizontal
line 1.5 cm apart, as shown. Figure 1: Example of the filter paper
sheets
www.LabPaq.com
152
©Hands-On Labs, Inc.
Experiment
Chromatography of food dyes
3.
On Sheet 1, from left to right, lightly label in pencil each
section between the cross lines with the abbreviation for the six
FD&C food colors from your experiment bag that will be
tested, i.e., B1, B2, R3, R40, Y5, and Y6.
4.
Also on Sheet 1, but now right to left, place the labels KG and KS
to represent the Kool-Aid® Grape and Kool-Aid®Strawberry
drink mixes to be tested.
5.
On Sheet 2 from left to right, lightly label in pencil each section
between the cross lines with the abbreviation for the grocery store
food colorings that will be tested, i.e., R, Y, G, and B.
6.
Also on Sheet 2, but now from right to left, place the label UK for
unknown and then M plus a letter for the color of four different
candies from your bag of M&Ms®, i.e., MR, MY, MB, etc.
7.
Set Sheet 2 aside and perform the following for Sheet 1. After you
have completed the experiment for Sheet 1, repeat for Sheet 2.
8.
For each dye on the sheet to be tested:
a.
First place a few drops in a well of the 24-well plate.
b.
Next, dip a clean toothpick tip into the dye and then briefly touch
the toothpick tip to the CENTER of the appropriately marked
section on the horizontal line on the filter paper.
c.
note 1: A small drop of water on a little bit of Kool-Aid®
powder will be sufficient to make a sample to spot the paper. A
small drop of water on the coating of an M&M® will dissolve
enough dye for the toothpick to pick up. The coating of blue
and brown M&Ms® is made up of very interesting dye
combinations!
d.
note 2: Apply only a small drop of each dye on the paper. Big
drops may spread over a greater area and overlap with other
dyes. This is called band broadening. Although a larger dot will
produce a more vivid color, a smaller dot will show the most
distinct break between colors.
Once the paper is spotted with all the dyes, allow the spots to dry
for a few minutes.
Figure 2: Procedure to form the paper into a cylinder
9. Now form the paper into a cylinder with the edges touching, but
NOT overlapped, and staple at the top and bottom as shown. (You
may want to use small pieces of tape on the outside to lightly hold
the cylinder together while you securely staple it. If so, remove the
tape after stapling.) Set the cylinder aside for a moment.
www.LabPaq.com
153
©Hands-On Labs, Inc.
Experiment
Chromatography of food dyes
10.
The salt water (~0.1% NaCl) you previously prepared will be your
eluting solvent and a petri dish will be your elution chamber. Pour
salt water into the clean and empty petri dish to a depth of about
1/2 cm. This is just enough to cover the bottom of the elution
chamber.
11.
Set your cylinder next to the petri dish with the spots at the bottom
and look to make sure the solvent level is below the line of dye
spots. If it is not pour out a little solvent until it is. The spots at the
bottom of the chamber must be above the solvent level for this
experiment to work well.
12.
Carefully drop the dye cylinder into the eluting chamber, making
sure not to touch the petri dish sides. The solvent-front will travel
up the paper rapidly at first and then will slow down. Let the
solvent-front rise for a few minutes, but immediately remove the
cylinder if any column moves up higher than 2 cm from the top of
the paper. If all the solvent is soaked up before the front has time to
move toward the top of the paper carefully add a little more solvent
to the petri dish.
13.
When complete remove the cylinder from the chamber and
immediately mark the top of each solvent-front with a pencil.
Allow the paper to dry for several minutes.
14.
Then measure to the nearest millimeter and record the heights of
the dye and solvent-front in each column:
a.
Start from the original horizontal pencil line and measure to the top
center of where the dye stops in each column on the paper. Record.
b.
Measure the heights of the solvent-front for each column from the
original horizontal pencil line to the lines drawn in Step 14.
Record.
15.
Calculate and record the Rf value for each spot: Rf = dye
distance/solvent distance
16.
Repeat Steps 8 through 15 for the items listed on Sheet 2.
17.
By comparing the color columns of the unknown sample and the
food items with those of the FD&C food dyes it is possible to
determine which dyes are used in the Kool-Aid®, in the grocery
food colorings, and in the M&Ms®. Identify the following:
a.
The FD&C color(s) making up the unknown,
b.
The FD&C color(s) making up the grocery store food colorings.
Don’t forget to indicate the brand name; e.g., Kroger®,
McCormick®, etc., and
c.
The FD&C color(s) making up the Kool-Aid® drinks and
M&M’s®.
www.LabPaq.com
154
©Hands-On Labs, Inc.
Experiment
Chromatography of food dyes
Chromatography of Food Dyes
Peter Jeschofnig, Ph.D. Version 42-0148-00-01
lab rEpOrt assistant
This document is not meant to be a substitute for a formal
laboratory report. The Lab Report Assistant is simply a summary
of the experiment’s questions, diagrams if needed, and data tables
that should be addressed in a formal lab report. The intent is to
facilitate students’ writing of lab reports by providing this
information in an editable file which can be sent to an instructor.
ObsErvatiOns
Enter data tables, observation questions from the procedures and
descriptions of diagrams to be drawn or pictures to be included
here, one per text box.
Data
Table
Sheet
1:
FD&C
Food
Colors
Color
blue1
blue2
red3
red40
yellow5 yellow6 Solvent
Distanc
e (mm)
rf
Data Table Sheet
1: Drink Mixes
Kool-Aid®
Grape
substance
Kool-Aid®
Strawberry
Solvent
Distance (mm)
Distance (mm)
rf
www.LabPaq.com
155
©Hands-On Labs, Inc.
Experiment
Chromatography of food dyes
Data Table
Sheet 2:
Store Food
Colors
substance
store red
store
yellow
store
Green
store
blue
Solvent
Distance
(mm)
rf
Data Table
Sheet 2:
Candy
Colors
substance
M&M
Green
M&M
Yellow
M&M
Blue
M&M
Red
Distance
(mm)
rf
www.LabPaq.com
156
©Hands-On Labs, Inc.
Experiment
Chromatography of food dyes
QuEstiOns
A. Why can’t a pen be used to draw the baseline on the
chromatography paper?
B. Why is it important to stop the chromatograph before the
solvent reaches the top of the paper?
Solvent
C. Why is it important to keep the dye spots above the solvent
level?
D. Why is it important to mark the solvent level on the
chromatography paper when you remove it from the petri dish?
-
Rating:
/5
Solution: the safety materials and wear goggles when working