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. Background Information • 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 siliconbased 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 Background Information • 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. Procedure 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 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 Resistance Measured ( Kilo Ohms ) Minus the Resistance Measured for Water Subtracted Resistance Values Measured for Blue Dye (kilo ohms) versus Known Concentrations of Blue Dye ( Micromolar ) 7 6 y = 0.2458x0.762 R² = 0.9716 5 4 3 2 1 0 0 10 20 30 40 50 Concentration of Blue Dye ( Micromolar ) 60 70 80 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 Equation used y = 0.2458x0.762 Drink Average concentration (Micromolar) MVP 8.31 Powerade 6.19 Gatorade G2 Series 2.58 Gatorade G Series 1.76 Resistance ( kiloohms ) measured over a period of time for blue dye mixed with bleach 1 Drop of Bleach 2 Drops of Bleach 4 Drops of Bleach Initial 1 min 2 min 3 min 4 min 5 min 7 min 9 min 11 min 13 min 15 min 17 min 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 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 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 ) Initial 1 min 2 min 3 min 4 min 5 min 7 min 9 min 11 min 13 min 15 min 17 min 5.353 4.093 2.783 2.103 1.543 1.113 0.213 0.213 0.123 0.043 0.013 0.003 1 Drop of Bleach 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 5.923 3.303 1.783 0.933 0.473 0.243 0.053 0.013 2 Drops of Bleach 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 5.943 1.823 0.583 0.233 0.153 0.133 4 Drops of Bleach 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 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 2 Drops of Bleach 4 Drops 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 68 32.21 15.63 7.48 3.47 1.72 0.46 0.27 68 13.3 2.61 0.59 0.21 0.14 Average Concentration ( micromolar ) of blue dye mixed with bleach over a period of time 80 Concentration( Micromolar ) 70 60 50 40 30 20 10 0 0 2 4 6 8 10 Time ( Minutes ) • • • • Black Line/Blue Diamonds : 1 Drop of Bleach Orange Line/Green Triangles: 2 Drops of Bleach Green Line/Black Squares: 4 Drops of Bleach • • • • 12 14 16 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 18 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.