Personal Narrative CEM 161
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Project 3 Personal Narrative: Food Dye Spectroscopy
Anna Wroblewski
Claim
Our team is working for a discount beverage company that produces off-brand versions
of popular sodas and fruit drinks. The United States has seven dyes that are approved for food,
drug, and cosmetic (FD&C) products at low concentrations. We were given the UV-Vis
absorbance spectrum for each of these seven dyes in our General Chemistry Laboratory
Manual. Secondly we were given a 10mL sample of this new “name-brand” sports drink with two
of these dyes in its concentration. Our goal as a team was to figure out which two dyes were in
our given solution of this drink, find the absorption and concentration of the dyes, and recreate a
10mL solution to match as similar to the name-brand product as possible using the FD&C dyes
as well as their profiles on the UV-Vis Absorbance Spectrum to replicate a similar beverage
color profile. After we created our replicated solution we were tasked with testing the success of
our solution on the UV-Visible spectroscopy machine.
Resources
Laboratory Technique Guides
●
Diluting Solutions
●
Measuring Liquids by Volume
●
Standard Curves
●
UV-Vis spectroscopy
●
Statistics and Calculations (in
Spreadsheets)
Course Technology Guides
●
Uploading Handwritten Contest to
D2L
●
Vernier Software and Devices
●
Graphing (in Excel)
Assignment Guides
●
Experiment Preparation and Design
●
Scientific Notebooks
●
Scientific Reporting
●
CATME Surveys
Project Materials
●
(10mL) Unknown beverage solution
●
(25L) FD&C Blue #1 solution
●
(25L) FD&C Red #3 solution
●
RO/DI Water
●
KimWipes
●
PPE
●
(2) 5.00 mL Serological pipet
●
(2) 10.00 mL Serological pipet
●
(2) Pipet filler
●
(4) 10.00 mL Volumetric flask
●
(1) Vernier Sensor Kit B
○
(1) Vernier SpectroVis+
spectrophotometer
○
(1) Plastic cuvette
○
(1) Cuvette holder
○
(1) USB-A/C cord
○
(1) Power supply
Evidence
Goal 1
After we were given our 10 mL solution that we are trying to recreate, we had to set up
our Vernier Sensor Kit B.This sensor kit is used to analyze the chemical properties of a material,
in this case FD&C dye, by measuring the amount of UV or visible light wavelengths absorbed
through a sample in comparison to our controlled sample. We first measured our control, RO/DI
water in the machine by using a serological pipette to insert the water into the plastic cuvette
that was included in the kit. After we got the absorbance and wavelength of our control, we
moved on to measuring the given solution in the same way we measured the RO/DI water.
Figure 1:
UV-Vis Absorbance Spectrum
for Red #3 and Blue #1 dye.
When we tested the 10 mL solution
that was given to us the UV-Visible
spectrophotometer machine gave us a graph.
The first peak was at around 1.126
absorbance and a wavelength of 527.1 nm,
and the second peak's absorbance was at
0.898 with a wavelength of 627.7 nm. Once
we had the graph and the properties of the
two peaks, we were able to compare it with
the seven dye UV-Vis Absorbance Spectrum
graphs in our General Chemistry Laboratory
Manual (shown in
figure 1
). From here we
found that the first peak from our given solution matched the absorbance and wavelength of dye
Red #3 and the second peak matched that of dye Blue #1. With this information we were able to
determine that these two dyes were present in our given solution, and we concluded that we
only needed to use these two dyes in order to replicate the solution.
Goal 2
After learning what two dyes were present in our given purple solution, we now needed
to determine the concentration of the Red #3 and Blue #1 dyes within the 10 mL purple sample.
In order to find the concentration within the purple solution, we needed to test for the
concentration of each the Red #3 and Blue #1. We ran four tests on both Red #3 and Blue #1
that consisted of 2 mL dye and 8 mL RO/DI water, 4 mL dye and 6 mL RO/DI water, 6mL dye
and 4 mL RO/DI water, and 8 mL dye and 2 mL RO/DI water. Once we gathered that information
we used the equation M1V1 = M2V2 to solve for the concentration of each dye in the four tested
solutions.
Test
Number
Concentration
of Dye
Concentration of
RO/DI Water
Concentration of
Red #3
Absorbance
of Red #3
Concentration
of Blue #1
Absorbance of
Blue #1
Test 1
2 mL
8 mL
6.32x10^-7
0.492
1.712x10^-6
0.171
Test 2
4 mL
6 mL
1.264x10^-6
0.962
3.424x10^-7
0.371
Test 3
6 mL
4 mL
1.896x10^-6
1.243
5.136x10^-7
0.539
Test 4
8 mL
2 mL
2.528x10^-6
1.392
6.848x10^-7
0.718
Figure 2:
represents the absorbance and concentration calculated from each of the 4 solutions
with different concentrations of dye for each dye color.
We graphed these numbers shown in
Figure 2
on an excel spreadsheet and got a linear
graph, which we then found the epsilon. The epsilon for Red #3 was 0.14905 and the epsilon of
Blue #1 was 0.09054. Now that we have our
, we used the equation C = A/
to find the
Ɛ
Ɛ
concentration of each dye in our purple solution. From this equation, we learned that the
concentration of Red #3 in the purple solution was 7.5545 and the concentration of Blue #1 was
9.928.
Goal 3
Once we found the concentration of each dye in our purple solution we once again used
the equation M1V2 = M2V2 in order to calculate the
amount of blue and red dye we need to create a 10 mL
replica solution(shown in
Figure 3
). From the numbers
we gathered we put 0.9928 mL of Blue #1 into a
volumetric flask and 0.7554 mL of Red #3 into the same
volumetric
Figure 3:
shows
the calculations that formed our answer for the amount
of dye needed in our 10 mL replicated solution.
flask and filled the rest of the flask with RO/DI water up
to the 10 mL line. After creating the replica solution, we
then tested it in the UV-Vis+ machine to see how close
of a match it was to the initial purple solution that was
given to us. We calculated the percent yield to find out
how accurate the concentration of the dyes inside the
replicated solution was.
Figure 4
below shows how
inaccurate our re-created solution was, although it had a
similar color, the concentration of the amount of dye in
both solutions was way off. We assumed that the inaccuracy of our results was due to human
error, and mechanical difficulties from using the UV-Visible spectrophotometer.
Figure 4:
shows the percent yield of the concentration of dye in our replicated solutions
compared to the concentration of dye that was in our given solution.
Reasoning
The absorption of light in terms of using the UV-Visible spectrophotometer machine is
controlled by the certain characteristics of what is in a specific substance. For our experiment,
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the absorption of light would be guided by the molecular characteristics of each of the dyes
present in our tested solution. Within dyes there are systems of molecules that have singular,
double and triple bonds which allow certain wavelengths of light to be absorbed and reflected.
The colors that are absorbed are predetermined by the amount of energy each certain color, or
dye, needs to absorb a photon of light.
The relationship between the absorbed wavelength and the concentration of dye in a
solution is described by the Beer-Lambert Law. This law states that the absorbance of light by a
solution is directly proportional to the concentration of the absorbing substance and the path
length of light through the solution:
A
=
ε
⋅
l
⋅
c.
A describes the absorbance of the solution,
ε
describes the molar absorptivity or the slope that we determined depicted in
Figure 2
, l is the
path length of light through the solution which in our case was one, and c which is the
concentration of the absorbing dye. By using this equation we were able to determine the
concentration of dyes in our given purple solution, and the concentration of the dyes in our
replicated solution.
As shown in
Figure 4
our calculated concentration was very inaccurate when compared
to concentration of dye in our given solution. While the color was very similar, there was an
immense amount of more dye present in the given solution than our replicated solution. This
could be due to the fact of the inevitability of human error as well as the difficulty our team had
with the UV-Visible spectrophotometer.
References
1.
The General Chemistry Laboratory Manual (Fall 2023), Pages 102,105
2.
Course Resources - UV-Visible Spectroscopy
https://d2l.msu.edu/d2l/le/content/2037655/viewContent/14727097/View
3.
Course Resources - Diluting Solutions
https://d2l.msu.edu/d2l/le/content/2037655/viewContent/14727094/View
4.
Assignment Guides - Scientific Reporting
https://d2l.msu.edu/d2l/le/content/2037655/viewContent/14727075/View
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