ROSETTA Colorimeter

Making a Colorimeter to Determine

Blue Dye Concentration

Arun Pidugu

10th Grade

Methacton High School

Problem Question: Can a simple, electronic

device functioning as a colorimeter be used to

determine the unknown concentration of blue dye

in sports drinks and also study the rate of a

chemical reaction involving blue dye.

Background Information

• A colorimeter is a device that measures the absorbance of light by a colored

solution.

• It has many applications, such analyzing of water quality or finding the hemoglobin

content in blood.

• A colorimeter can be used to find the concentration of blue dye in sports drinks

because according to Beer-Lambert’s Law, the concentration of a substance in a

solution is proportional to the absorbance of light by the solution.

• FD&C Blue 1, which is used in this study, is a dye commonly found in foods and

drinks.

• Dyes can cause allergic reactions in individuals who suffer from allergies or asthma

and they are also harmful when consumed in high concentrations.

• Due to the fact that many people consume sports drinks which are colored with

dyes, I have decided to build a electronic device that functions as a colorimeter to

determine the unknown concentration of blue dye in sports drinks.


• A dye-sensitized solar cell is a type of solar cell that is based on a semiconductor

formed between a photo-sensitized anode and a liquid electrolyte

• It belongs to a group of solar cells known as thin-film photovoltaic cells, which

means that they are constructed by depositing one or more layers of light-absorbing

materials on a substrate

• Because they are cheaper, lighter, and easier to manufacture than regular silicon-

based solar cells, they are considered to be a viable new energy-source, especially

in regards to developing countries

• The dye-sensitized solar cells created in this experiment


• An LED and a photoresistor are aligned on a breadboard in a straight

line & they are covered in cuvettes. Cuvettes containing orange dye

solution (which acts as a filter) and the blue dye sample are placed

between them.

• The filter is used because it makes the light from LED orange colored

and the color orange is strongly absorbed by the blue-colored

solution

• The electronic device constructed in this experiment measures

resistance, instead of absorbance.

• The resistance measured is proportional to the absorbance of light by

the solution, and therefore proportional to the concentration of blue

dye. As more light is absorbed, less light is detected by the

photoresistor so its resistance is larger.

Hypothesis: The concentration of blue dye

in sports drinks and the rate of chemical

reactions involving blue dye can be

determined by a homemade colorimeter.

Materials

• Solderless breadboard socket

• Insulated test/jumper leads, 24-inch

• 9-V batteries

• Heavy-duty 9-V snap connectors

• Photoresistor

• Ultra-high-brightness LED

• Resistor, 220-ohm

• Digital multimeter

• Cuvettes

• Durkee Blue Food Color ( FD&C

Blue 1 )

• Durkee Yellow Food Color

• Durkee Red Food Color

• Cups

• Graduated Cylinder

• Masking tape

• Measuring spoons

• Eyedropper

• Stopwatch

• Clorox Bleach

• Safety goggles

• Latex gloves

• Plastic wrap

• Sports Drinks Containing FD&C Blue 1

• Gatorade G Series Frost Glacier

Freeze

• Powerade

• Gatorade G2 Series Glacier Freeze

• MVP Blue Freeze ( Store Brand )

Variables

• Control Group: Distilled Water

• Independent Variables: The different drinks tested in

this experiment and the amount of bleach used.

• Dependent Variable: The resistance measured by the

multimeter.

• Constants: Voltage of the battery, Volume of solution

placed in the cuvette, Orange Filter, LED &

Photoresistor used, Absence of Stray Light, and

Temperature

Procedure

A. Building the Colorimeter

1. Attach the battery to a snap connecter, connect red wire to power bus & black wire into

ground bus on a breadboard.

2. Insert the LED & Photoresistor into the breadboard so that they are aligned in the

middle of the breadboard and the top of the photoresistor is bent so that it is facing the

LED.

3. Cover the LED & Photoresistor in cuvettes and make sure there is enough space in

between them to tightly fit 2 other cuvettes.

4. Place one end of the 220-ohm resistor into the same row as the LED and the other into

the ground bus. Place one end of a white jumper wire in the same row on the opposite

side of the LED and the other into the power bus

5. Place two white jumper wires on opposite sides of the photoresistor in the same row.

Attach the multimeter to these wires.

B. Preparing Blue Dye Solutions with Different Concentrations

1. Set out 7 cups, label them #1-7 for different dilutions – 1, ½, ¼, 1/8, 1/16, 1/32 and 1/64

2. Pour 237 ml of water into the cup #1 and 118 ml of water into the rest.

3. Mix 0.62 ml of blue dye in cup #1 – most concentrated

4. Pour 118 ml of liquid from cup #1 into cup #2, pour 118 ml from cup #2 into cup #3,

and follow this pattern until cup #7 to get various dilutions

5. Label a cup #8 and fill w/ water.

C. Preparing Orange Filter

1. Pour 118 ml of water into a cup

2. Add two drops of red & yellow dye and mix thoroughly to make the orange dye

solution.

Procedure

D. Measuring Concentrations

1. For all measurements, set the multimeter to measure the resistance in kilo ohms

2. Fill a cuvette w/ the orange dye and place it in front of the LED

3. Fill cuvettes w/ a sample from cups #1-8

4. To measure resistance, place the cuvette containing the sample between the

filter & photoresistor and make sure all sources of light except the LED are

turned off.

5. Measure & record the resistance for all eight concentrations

6. Repeat this process with sports drinks

Procedure

Procedure

E. Studying Chemical Kinetics to Observe the Rate of Color Loss

1. Fill 3 cuvettes w/ water and for each, measure the resistance then put one

drop of bleach into the water, mix, and record resistance again.

2. Use the most concentrated blue dye solution in this study

3. For each sample, measure the initial resistance then put one drop of bleach

into the solution, mix, and record resistance every minute for 5 minutes, then

every two minutes until the resistance stops changing, indicating the color

loss is complete.

4. Repeat this process w/ two & four drops of bleach

F. Calculations

1. Using Excel, graph the resistance values measured for the known

concentrations of blue dye w/ concentration on the x-axis and resistance on

the y-axis.

2. Use the trend line feature and graph the trend line which has the R2 value that

is closest to 1. The R2 value represents how well a line fits a set of points and

the closer it is to 1, the better the line fits the set of points.

3. The equation of the trend line will be used to find unknown blue dye

concentrations.

Resistance (kilo ohms) measured for known concentrations of blue dye

Dilution Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Average Standard

Deviation

Most

Concentrated

( 68 µM ) 8.59 8.61 8.75 8.66 8.74 8.67 0.00535

½ Dilution

( 34µM ) 6.12 6.01 5.99 6.07 6.13 6.064 0.00398

¼ Dilution

( 17 µM ) 4.53 4.48 4.35 4.39 4.52 4.454 0.00517

1/8 Dilution

( 8.5 µM) 3.66 3.62 3.56 3.66 3.56 3.612 0.0252

1/16 Dilution

( 4.25µM ) 3.3 3.24 3.23 3.19 3.45 3.282 0.01037

1/32 Dilution

( 2.125 µM ) 3.02 3.09 3.00 3.04 3.03 3.036 0.00113

1/64 Dilution

( 1.0625 µM ) 2.66 2.67 2.74 2.63 2.62 2.664 0.00223

Water Only 2.51 2.41 2.45 2.44 2.53 2.468 0.00252

Resistance (kilo ohms) measured for known concentrations of blue dye

minus resistance measured for water ( 2.468 kilo ohms )

Dilution Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Average Standard

Deviation

Most

Concentrated

( 68 µM ) 6.122 6.142 6.282 6.192 6.272 6.202 0.00535

½ Dilution

( 34µM ) 3.652 3.542 3.522 3.602 3.662 3.596 0.00398

¼ Dilution

( 17 µM ) 2.062 2.012 1.882 1.992 2.052 2.00 0.00517

1/8 Dilution

( 8.5 µM) 1.192 1.152 1.092 1.192 1.092 1.144 0.0252

1/16 Dilution

( 4.25µM ) 0.832 0.772 0.762 0.722 0.982 0.814 0.01037

1/32 Dilution

( 2.125 µM ) 0.552 0.622 0.532 0.572 0.562 0.568 0.00113

1/64 Dilution

( 1.0625 µM ) 0.192 0.202 0.272 0.162 0.152 0.196 0.00223

y = 0.2458x0.762

R² = 0.9716

0

1

2

3

4

5

6

7

0 10 20 30 40 50 60 70 80

Res

ista

nce

Mea

sure

d (

Kil

o O

hm

s )

Min

us

the

Res

ista

nce

Mea

sure

d f

or

Wate

r

Concentration of Blue Dye ( Micromolar )

Subtracted Resistance Values Measured for Blue Dye (kilo ohms) versus

Known Concentrations of Blue Dye ( Micromolar )

Resistance ( kilo ohms ) measured for unknown concentrations of blue dye in sports

drinks

Gatorade G

Series

Gatorade G2

Series Powerade MVP

Trial 1 2.76 3.03 3.41 3.72

Trial 2 2.83 2.91 3.52 3.67

Trial 3 2.84 2.98 3.45 3.7

Trial 4 2.93 2.97 3.46 3.69

Trial 5 2.87 2.98 3.43 3.73

Average 2.846 2.974 3.454 3.702

Resistance ( kilo ohms ) measured for unknown concentrations of blue dye in sports drinks minus

resistance measured for water ( 2.468 kilo ohms )

Gatorade G Series Gatorade G2 Series Powerade MVP

Trial 1 0.292 0.562 0.942 1.252

Trial 2 0.362 0.442 1.052 1.202

Trial 3 0.372 0.512 0.982 1.232

Trial 4 0.462 0.502 0.992 1.222

Trial 5 0.402 0.512 0.962 1.262

Average 0.378 0.506 0.986 1.234

Average concentration of blue dye in sports drinks

Drink Average concentration

(Micromolar)

MVP 8.31

Powerade 6.19

Gatorade G2 Series 2.58

Gatorade G Series 1.76

Equation used

y = 0.2458x0.762

Resistance ( kiloohms ) measured over a period of time for blue dye mixed with bleach

Initial 1 min 2 min 3 min 4 min 5 min 7 min 9 min 11 min 13 min 15 min 17 min

1 Drop of

Bleach

8.08 6.82 5.51 4.83 4.27 3.84 3.26 2.94 2.85 2.77 2.74 2.73

8.52 7.03 6.28 5.58 4.99 4.52 3.84 3.43 3.17 3.01 2.91 2.86

8.27 7.93 6.86 5.98 5.28 4.73 3.97 3.55 3.31 3.18 3.11 3.07

2 Drops of

Bleach

8.65 6.03 4.51 3.66 3.2 2.97 2.78 2.74

8.41 6.35 4.84 4.00 3.46 3.18 2.91 2.84

8.81 6.23 4.79 3.89 3.38 3.11 2.88 2.86

4 Drops of

Bleach

8.67 4.55 3.31 2.96 2.88 2.86

8.99 4.41 3.16 2.83 2.74 2.73

8.96 4.48 3.20 2.86 2.77 2.75

Resistance ( kiloohms ) measured over a period of time for blue dye mixed with bleach minus resistance measure for

water( 2.7267 kilo ohms )


1 Drop of

Bleach

5.353 4.093 2.783 2.103 1.543 1.113 0.213 0.213 0.123 0.043 0.013 0.003

5.793 4.303 3.553 2.853 2.263 1.793 1.113 0.703 0.443 0.283 0.183 0.133

5.543 5.203 4.133 3.253 2.553 2.003 1.234 0.823 0.583 0.453 0.383 0.343

2 Drops of

Bleach

5.923 3.303 1.783 0.933 0.473 0.243 0.053 0.013

5.683 3.623 2.113 1.273 0.733 0.453 0.183 0.113

6.083 3.503 2.063 1.163 0.653 0.383 0.153 0.133

4 Drops of

Bleach

5.943 1.823 0.583 0.233 0.153 0.133

6.263 1.683 0.433 0.103 0.013 0.003

6.233 1.753 0.473 0.133 0.043 0.023

Average Concentration ( micromolar ) of blue dye mixed with bleach over a period of time


1 Drop

of

Bleach

68 45.38 32.37 23.64 17.00 12.17 5.25 3.19 1.86 1.13 0.77 0.60

2

Drops

of

Bleach

68 32.21 15.63 7.48 3.47 1.72 0.46 0.27

4

Drops

of

Bleach

68 13.3 2.61 0.59 0.21 0.14

Dt = Do e-at

• Dt = the concentration of dye at time, t (1

minute, 2 minutes, etc.)

• Do = starting concentration of dye

• e = Euler’s Number: 2.718

• a = slope, determined by experiment

• t = time, measured in minutes

0

10

20

30

40

50

60

70

80

0 2 4 6 8 10 12 14 16 18

Con

cen

trati

on

( M

icro

mola

r )

Time ( Minutes )

Average Concentration ( micromolar ) of blue dye mixed with bleach

over a period of time

• Black Line/Blue Diamonds : 1 Drop of Bleach

• Orange Line/Green Triangles: 2 Drops of Bleach

• Green Line/Black Squares: 4 Drops of Bleach

Conclusion

• The resistance measured in this experiment was directly

proportional to the blue dye concentration proving that this

colorimeter works in accordance with the Beer Lambert law.

• The calculated concentrations of blue dye mixed w/ bleach over

time, correctly modeled the exponential decay equation, further

proving that the homemade colorimeter is reliable.

• From the results, it can be seen that the store brand MVP sports

drinks had the highest blue dye concentration, 8.31µM

• The results confirm the hypothesis, which stated that the

homemade colorimeter can be successfully used in determining

the unknown concentrations of blue dye.

Possible Errors

• The photoresistor might have been slightly moved over the course of this

experiment, which would have caused the values measured by the

multimeter to have differed slightly

• The voltage of the battery could have decreased over time, causing a

change in the intensity of the light and therefore could have slightly altered

the resistance measured by the multimeter. To counter this the battery was

changed halfway through the experiment

Future Ideas

• A lab colorimeter could be used to determine the concentration of blue

dye in sports drinks and to see how the results compare with the results

of this experiment.

• To analyze the concentration of other dyes using different colored

filters, such as analyzing the concentration of red dye in sports drinks

using a blue-green filter.

Real World Applications

• Using the colorimeter to help in determining the concentration of

blue dye in sports drinks can be useful to find out if the

concentration is high enough to be potentially harmful.

• Individuals who are allergic to dyes can use this homemade

colorimeter to determine the unknown concentrations of the dyes in

various food products. Depending on their sensitivity level to the

dye, they can avoid products with high dye concentrations.

• The homemade colorimeter can also be used to accomplish useful

tasks such as testing water quality by helping screen for impurities

such as iron or zinc.

Documents

ROSETTA Colorimeter