Project 2: Food Dye in Commercial Products PDF

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Second formal lab report for the lab. The grade was 40/40. The paper has a 0% score on Turnitin. Received an A+ in the lab....

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Analyzing the Amount of Food Dye in Commercial Products CHML2045L

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Introduction The overall focus of the experiment was to identify and use a spectrophotometer to find the amount of dye in widely used commercial products. At the end of the experiment the concentration and absorption of dye in the product was determined. In addition, learning how to effectively use a spectrophotometer for chemical analysis was obtained. Background knowledge of serial dilutions, beer’s law, and spectroscopy were utilized to efficiently complete the lab. Spectroscopy is the measure of the intensity of a light beam passing through a solution (Libretexts, 2020). This concept is universally used for chemical analysis because it allows researchers to improve the components of drugs and examine the state of matter purities. UV – visible spectrophotometry focuses on light that goes through visible light on the electromagnetic spectrum. The visible light wavelength ranges from 400nm – 700nm. The ultraviolet range light is from 185-400nm. The colors on the spectrum are red, orange, yellow, green, blue, indigo, and violet. Violet light contains the shortest wavelength from 380-450nm while red light has the longest wavelength from 625nm-700nm. A spectrophotometer measures the absorbance of light. The device holds a cuvette that is analyzed into a spectrometer app. A calibration curves are used in discovering the unknown concentration of a sample (JoVE, 2021). The data values generated from UV – vis – spectroscopy is used to plot the curve. Majority of calibration curves are liner with a slope and r square value. Serial dilutions allow for the creation of the curve easier because each sample needs its own concentration. Beer's law is concerned with the connection between absorbance and concentration. Beer’s law plot serves as a function of concentration (Anderson, et.al., 2021). To develop the plot the maximum absorbance wavelength must be found. Each dye contains a lambda max which is the point where the wavelength has the highest photon absorption. There must be at least 5 solutions for the unknown concentration to be discovered.

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The formula for the relationship is A = ↋Cl = (y= mx + b) then C = A/l↋. The symbols in the formula mean: A is the absorbance,↋ for molar absorptivity, C is concentration, and l is path length (Anderson, et.al., 2021). Experimental Methods The materials utilized during the experiment were 3 cuvettes, 6 pipette pumps, graduated pipette, spectrophotometer, and general laboratory glassware (volumetric flask, 6 beakers, Erlenmeyer flask). The spectrometer was essential to the experiment because it is where the data is taken to create a calibration curve. The chemicals used were yellow dye #5 and green dye #3. The two commercial products chosen were Mountain Dew and Listerine cool mint. The first part of the experiment was completed by creation of 5 solutions for yellow #5 dye. Using the serial dilution technique, the solutions were made based on a 1:1 ratio. Once the yellow 5 dye (stock solution) was obtained using a graduated cylinder 50mL of the dye was measured out. Then once the dye was measured and put in the Erlenmeyer flask, diy water was added up to the 100mL mark. The solution in the flask served as solution A and was put into one of the 6 beakers. For the next 4 solutions the same procedures were repeated based on the 1:1ratio. After the 5 solutions (yellow #5) were made, absorbance values were measured using a spectrophotometer. The absorbance values had to be between 0.1 – 1.0 to be accurate. The spectrophotometer was calibrated using a black cuvette and clear cuvette with diy water. After this, each solution was placed into an empty cuvette to be inserted into the spectrophotometer facing the light source. The absorbance values were determined by measuring the lambda maximum of yellow 5 at 416nm. The second part of the experiment was to obtain the unknown concentration of the Mountain Dew. Cleaning the previously used cuvette, the mountain dew was poured into the cuvette up to the v mark and placed into the spectrophotometer. Once the yellow 5 dilutions were

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done, all the glassware was cleaned, and pipettes replaced. A serial dilution technique was conducted for green #3 dye. Using a graduated cylinder, 40mL of green 3 dye was added to the 100mL Erlenmeyer flask. Then diy water was added up to the 100mL mark to create a homologous solution and added to one of the 6 beakers. These steps were repeated for the remaining 4 solutions for green 3 dye. The solutions were made based on a 4:6 ratio, 40mL dye and 60mL of diy water. The spectrophotometer device was calibrated again and all 5 solutions of green dye 3 were analyzed. The absorbance readings of the solutions were read at the green dye 3 lambda max which was 605nm. In an empty clear cuvette, the mint fresh Listerine was placed into to the spectrophotometer to have its absorbance read. When the concentrations were calculated for both dyes, a concentration vs. absorbance graph was made for each. The unknown concentration for the products were calculated using the formula r = Mc + b. Results Table 1– Serial Dilution Yellow 5 Dye Sample

A or 1 B or 2 C or 3 D or 4 E or 5

Sample

Stock

Volume

Total volume

Concentration

Concentration

measured (mL)

(mL)

(M) 2.5 x 10-4 -4 1.25 x 10 -5 6.25 x 10 -5 3.125 x 10 1.5625 x 10 -5

(M) 5 x 10-4 -4 5 x 10 -4 5 x 10 -4 5 x 10 5 x 10-4

50 50 50 50 50

100 100 100 100 100

Calculations for Yellow 5 Dye Concentration (m1v1 = m2v2) A. ( 5 x 10-4 )(50) = (m2) (100) →

0.025 = 100

2.5 x 10

−4

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B. ( 2.5 x 10-4 )(50) = (m2) (100) →

0.0125 100

C. ( 1.25 x 10-4 )(50) = (m2) (100) →

0.00625 100

D. ( 6.25 x 10-5 )(50) = (m2) (100) →

0.003125 100

E. ( 3.125 x 10-5 )(50) = (m2) (100) →

1.25 x 10− 4

=

=

0.0015625 100

6.25 x 10−5

= 3.125 x 10−5 = 1.5625 x 10−5

Table 2 – Concentration and Absorbance for Yellow 5 Dye Sample A or 1 B or 2 C or 3 D or 4 E or 5 Mountain Dew

Absorbance 1.790 1.701 1.121 0.605 0.327 0.761

Unknown concentration calculation for Mountain Dew: r = Mc + b 0.879 = 5976.9x + 0.5298 → 0.3492 = 5976.9x = 5.8424936 x 10−5

Graph 1 – Yellow 5 Concentration vs Absorbance.

Concentration (M) 2.5 x 10-4 -4 1.25 x 10 -5 6.25 x 10 -5 3.125 x 10 1.5625 x 10 -5 −5 5.84 x 10

1

r = 0.879

2

r =0.7725

y = 5976.9x + 0.5298

Table 3 – Serial Dilution Green 3 Dye Sample

A or 1 B or 2 C or 3 D or 4 E or 5

Sample

Stock

Volume

Total volume

Concentration

Concentration

measured (mL)

(mL)

(M) 2 x 10-4 8 x 10 3.2 x 10- 5 -5 1.28 x 10 5.12 x 10 -6

(M) 5 x 10-4 -4 5 x 10 5 x 10-4 -4 5 x 10 5 x 10-4

40 40 40 40 40

100 100 100 100 100

Calculations for Green 3 Dye Concentration (m1v1 = m2v2)

A. ( 5 x 10-4 )(40) = (m2) (100) →

0.02 = 100

B. ( 2 x 10-4 )(50) = (m2) (100) →

0.008 = 100

−4

2 x 10

8 x 10

−5

1

0.0032 = 100

C. ( 8 x 10-5 )(50) = (m2) (100) → D. ( 3.2 x 10-5 )(50) = (m2) (100) →

E. ( 1.28 x 10--5 )(50) = (m2) (100) →

0.00128 100

3.2 x 10−5

=

5.12 x 10−4 100

1.28 x 10−5

= 5.12 x 10−6

Table 4 - Concentration and Absorbance for Green 3 Dye Sample A or 1 B or 2 C or 3 D or 4 E or 5 Listerine Cool Mint

Absorbance 1.368 1.303 1.219 0.991 0.503 0.549

Concentration (M) 2.0 x 10-4 -5 8.0 x 10 -5 3.2 x 10 -5 1.28 x 10 -6 5.12 x 10 −5 6.71 x 10

Unknown concentration calculation for Listerine cool r = Mc + b 0.681 = 2973.6x + 0.8806 → 0.1996 = 2973.6x = 6.712402475 x

Graph 2 – Green 3 Dye Concentration vs. Absorbance

10−5

1

r = 0.681

r 2 = 0.4637

y = 2973.6x + 0.8806

Discussion Table 1 and 3 are the data values obtained during the lab using the serial dilution technique. The formula

M 1 V 1=M 2 M 2

was used to find the M 2 , which is the

concentration of the diluted solution. The original solution

M1V 1

represents the volume and

concentration. Since the stock solution concentration, original solution, and dilution volume was known, the data values were easily substituted into the equation. The concentration calculations for green 3 and yellow 5 dye represents the mathematical part of the diluted solution. In table 2, the results for yellow 5 dye absorbance and concentration were recorded. The absorbance values are read from the lambda max of the yellow 5 dye which was 416nm. Typically, the lambda max for yellow 5 dye is 480nm. The absorbance values were not between the range 0.1 – 1.0 meaning the solution was not diluted enough. Once the diluted solution concentration was calculated, the values were used to make a graph. According to Graph 1 – Yellow 5 dye concentration vs.

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absorbance, the linear equation of yellow 5 dye was y = 5976.9x + 0.5298. The equation represents a linear regression analysis to find a suitable equation for the calibration curve. The 5976.9x and 0.5298 are the constants for the expected slope and y-intercept. The r value was 0.879 and r 2

was 0.7725. The r value constitutes as a correlation coefficient based on how

well the equations fits the graph. When

r

2

is closer to 1 that means the equation fits the line

best. The r-squared value in, “Yellow 5 Concentration vs Absorbance” is 0.7725 meaning the equation fit the line somewhat. The relationship between concentration and absorbance is as the concentration of a sample increases the absorbance increases as well. In other words, the beer’s law theory states the solution’s concentration and absorbance are proportional. Beer’s law equation is A = ↋lc which is the same as the equation for a straight-line y = mx + b (Bellevue, 2014). The slope m is equal to ↋l because the path length is the same as the direction of the line. To find the concentration, the slope (m) was divided by the r value, but the y-intercept (b) had to be subtracted first. The reason for this was because the y-intercept is the starting point of the line. According to “Graph 2 – Green 3 Dye Concentration vs. Absorbance”. The liner equation was y = 2973.6x + 0.8806. The 0.8806 is the y-intercept symbolizing the starting point of the slope. The slope is 2973.6 which is the direction and steepness of the line. The r and r squared values were 0.681 and 0.4637. The r squared value (0.4637) is far from 1.00 meaning the equation is not the best fit for the line. During the lab, several possible sources of error could have occurred for instance, cross-contamination, improper dilution measurements, calculations errors from rounding, etc. There are some procedures that would have needed to be repeated in order to fulfill the objective. The first procedure needed to be repeated was the serial dilution technique in terms of diluting the solution more. For the green 3 and yellow 5 dye, the absorbance values were not in the proper ranges. The new dilution ratios would be 1:10 or 3:2 in order to produce

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appropriate absorbance values. Another procedure that would have been done differently, comparing the lambda max and data with other students with a similar dye. This would increase the reliability of the experiment and allow for identification of possible errors. Conclusion In summary, the purpose of the experiment was to calculate the concentration of food dye in a commercial food product using serial dilution and a spectrophotometer. Analyzing the amount of food dye concentrated in a product allows researchers to determine whether it is safe. The unknown concentration for Mountain Dew was 5.84 x 10^ (-5) with an absorbance of 0.761. The unknown concentration for Listerine cool mint was 6.71 x 10^ (-5) with an absorbance of 0.549. The equation for the yellow 5 graph fit the line somewhat while the green 3 equation was not the best fit of the line. The ratios for the experiment needed to be adjusted because the absorbance ranges were inaccurate. The absorbances were too large and would require a larger amount of water to dilute the stock.

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References Anderson, L., Figueroa, J., Lykourinou, V. General Chemistry 1 Laboratory Manual, 3rd ; University of South Florida: Tampa, FL, 2019; p34. Bellevue College. Beer’s law: Determining the Concentration of a Solution. (2014). https://www.bellevuecollege.edu/wp-content/uploads/sites/140/2014/06/161lab_Beers-Lawupdated-1-2-2014.pdf. (Accessed Jun 22,2021). JoVE Science Education Database. Calibration Curves. JoVE, Cambridge, MA, (2021). https://www.jove.com/v/10188/calibration-curves. (Accessed Jun 20,2021). JoVE Science Education Database. Introduction to the Spectrophotometer. JoVE, Cambridge, MA, https://www.jove.com/v/5038/introduction-to-the-spectrophotometer. (Accessed Jun 20,2021). Linear Regression and Calibration Curves https://chem.libretexts.org/@go/page/132505 (accessed Jun 21, 2021). Serial Dilutions and Standard Curve https://bio.libretexts.org/@go/page/36750 (accessed Jun 20, 2021). Spectrophotometry https://chem.libretexts.org/@go/page/1431 (accessed Jun 19, 2021)....