Spectrophotometric Analysis of Aspirin PDF

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Spectrophotometric Analysis of Aspirin Megan Alagna and Veronica, November 19, 2019, Chemistry 111-008, Dr. Lin, TA Nick

Introduction Aspirin is one of the most commonly used pain relievers because of its effectiveness and its active ingredient, acetylsalicylic acid. This over-the-counter drug is used to treat inflammation, fever, headaches, muscle aches, and various other symptoms. Aspirin, a member of the non-steroid antiinflammatory drug family (NSAIDs), deactivates the enzyme cyclooxygenase (COX), which is responsible for the synthesis of prostanoids, including prostaglandins (PGs) that cause swelling, fever, pain, and inflammation.1 It quickly became popular throughout the world in the 1900s, becoming the most popular painkiller in the Guinness Book of World Records in 1950 and brought on the first spaceship to the Moon in 1969. Earlier versions of aspirin include the use of willow leaves, myrtle leaves, and other extracts of

plants.2 Today, it comes in the form of tablets, liquids, and powders. Some side effects of aspirin may include gastrointestinal bleeding and digestive complications if taken in large quantities, so it is best to take the recommended dosage of aspirin that primary care providers and pharmaceutical companies suggest.3 This experiment will determine the amount of acetylsalicylic acid (ASA) in a standard aspirin tablet using spectrophotometric analysis of a solution containing acetylsalicylic acid and iron (III) ion, which forms a purple solution that can determine the quantification of aspirin through the color intensity using a colorimeter and LabQuest2. Using Beer-Lambert’s Law, which is an equation that states that absorption of light is independent of its intensity and that the amount of light absorbed is directly related to the number of

molecules of absorbing substance through

Values were adjusted for the stock solution

which the light passes, absorbance can be

concentration (1.99 x 103 mg/L) according

determined.4

to the amount measured, which was .498

𝐴=𝜖𝑏𝐶

(Eq. 1)

grams. The wavelength for this experiment

The addition of the iron (III) creates the

was measured at 536.5 nanometers (nm)

complex found in Equation 2.4

within the 500-550 nm range in order to find absorbance. Results

(Eq. 2) The linear equation provided by the

Table 1 Mass/Concentration of ASA and Aspirin Tablet

LabQuest2 using data from stock solutions

Acetylsalicylic Aspirin

of salicylate dianion, formed by aspirin

Acid

Tablet

39.401 g

31.408 g

39.899 g

31.787 g

0.498 g

0.379 g

reacting with sodium hydroxide, will

Mass of flask

provide the necessary data in order to

(g)

calculate the actual amount of acetylsalicylic

Mass of flask

acid in a standard aspirin tablet. This

and

complex is shown in Equation 3.4

compound (g) Mass of compound (g)

(Eq. 3) Experimental

Concentration

1.99 x 103

of ASA in

mg/L

stock solution All of the steps of the experiment were followed according to the lab manual.4

(mg/L)

After taking the masses of both the ASA and

The linear equation (y=mx+b) for the

aspirin solutions, the concentrations of five

concentration and absorbance of ASA was

amounts of ASA were taken as directed in

used as a guide to determine the

the Lab Manual.4 The concentrations and

concentration and absorbance of the

absorbances of each amount of stock

unknown solution of aspirin.

solution were used to determine the linear equation in Figure 1. Table 2 Concentration and Absorbance of Solutions

𝑦 = 0.0059857𝑥 − 0.027239

(Eq. 4)

The interpolation value of aspirin was used to find a concentration of 53.8 mg/L and the

Solution

Conc. (mg/L) Absorbance

A

39.8 mg/L

0.210

B

59.7 mg/L

0.322

C

79.6 mg/L

0.466

absorbance was plugged into the linear

D

99.5 mg/L

0.564

equation, the x-value was 53.8 mg/L, which

E

119.4 mg/L

0.685

Unknown

53.8 mg/L

0.295

absorbance was found at 0.295 when inserted into the spectrovis. When the

is the same as the interpolation value. The

(interpolation

concentration of the unknown aspirin

value)

solution was then used to determine the

Figure 1 Concentration and Absorbance of ASA in a linear equation

amount of ASA in grams using a standard value (325 mg) provided by the lab manual.4 𝑚𝑔 10−3 𝐿 (50.0 ) = 2.69 𝑚𝑔 (53.8 ) 𝑚𝐿) ( 1𝑚𝐿 𝐿 (Eq. 5) 2.69 𝑚𝑔 × 250.0 𝑚𝐿 = 336.25 𝑚𝑔 2.00 𝑚𝐿 = .336 𝑔

(Eq. 6)

By dividing the measured number of grams

536.5 nm was found in the green section of

in the aspirin tablet by the amount found in

the color spectrum, which is directly

the unknown concentration, a percentage of

opposite of the color purple on the color

88.7% ASA was determined.

wheel.

. 336 𝑔 × 100% = 88.7% . 379 𝑔 (Eq. 7)

Percent error was 3.38% using 325 mg as the theoretical and 336 mg as the experimental. Figure 2 The color wheel 336.25 𝑚𝑔 − 325 𝑚𝑔 × 100% = 3.38%. 325 𝑚𝑔 (Eq. 8)

The class average for the mass of aspirin in the tablet was 365 mg, and the average

Discussion percent of ASA in the tablet was 96.9%. The The amount of acetylsalicylic acid in the average percent error was 10.30%, which is given aspirin tablet, which had a mass of higher than the percent error of this 379 mg, was 336 mg as shown in Equation experiment (3.38%). Possible errors could 6. This meant that 88.7% of the aspirin have occurred during the selection of the tablet was acetylsalicylic acid. The wavelength (536.5 nm) or during usage of acidification of the iron (III) ion to change the cuvette, where it could have become the color of the concentrations to purple was foggy. The data might have been more used with the knowledge of the differing accurate if a different wavelength was wavelengths of the color wheel. A value of selected. By using spectrophotometry to

determine the amount of an unknown

found and what was shown in the resulting

substance in a compound such as ASA in

measurements.

aspirin, other substance amounts can also be determined using this method and can help

References

pharmaceutical companies measure the

(1) Vane, J.R.; Botting, R.M.; The

correct amount of active ingredient to add to

Mechanism of Action of Aspirin;

a given medicine.

Thrombosis Research; Volume 110, Issues 5-6; June 2003, pp. 255-258.

Conclusion

https://www.sciencedirect.com/science/articl

6 solutions were measured using a

e/pii/S0049384803003797

spectrophotometer to determine the amount

(2) Jack, D.B.; One Hundred Years of

of acetylsalicylic acid, the active ingredient

Aspirin; The Lancet; Volume 350, August

in aspirin. Solutions A-E were created using

9, 1997, pp. 437-439.

only ASA while the sixth unknown solution

https://www.thelancet.com/journals/lancet/ar

was created using an aspirin tablet. The

ticle/PIIS0140-6736(97)07087-6/fulltext

concentrations of solutions A-E were used to

(3) Huang, E.S.; Strate, L.L.; Ho, W.W.;

then determine an interpolation value for the

Lee, S.S.; Chan, A.T. Long Term Use of

unknown aspirin solution, which was then

Aspirin and the Risk of Gastrointestinal

used to calculate the percent of ASA

Bleeding; The American Journal of

(88.7%) and amount in milligrams of ASA

Medicine, May 2011,

(336 mg). The given amount on the label of

https://www.ncbi.nlm.nih.gov/pmc/articles/P

the aspirin was 325 mg, which shows an

MC3086018/.

inconsistent amount between what was

(4) Spectrophotometric Analysis of Aspirin; Chem 111 Laboratory Manual Fall 2019, pp. 43-48...