Determination of Acetylsalicylic Acid (ASA) Content in Aspirin Tablets

Abstract

The aim of this experiment was to determine the actual amount and percentage of acetylsalicylic acid (ASA) in an aspirin tablet. This information is crucial to ensure that individuals are taking the recommended dosage. The experiment involved the use of a UV-Vis spectrophotometer connected to a LabQuest2 to measure the absorbance of different ASA concentrations. The ASA concentrations were prepared by reacting acetylsalicylic acid with NaOH to produce the salicylate dianion, which was then quantitatively transferred and mixed with an iron (III) chloride solution to create the standard solution.

Five different concentrations of this solution were analyzed using the UV-Vis spectrophotometer to determine the absorbance of the violet tetraaquosalicylatroiron (III) complex. A calibration curve was created from the absorbance and concentration data, and this curve was used to calculate the amount of ASA and its percentage in the aspirin tablet.

Introduction

The active ingredient in aspirin tablets is acetylsalicylic acid (ASA). ASA is commonly used to relieve pain, reduce fever, and thin blood.

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It is essential to determine the actual amount of ASA in a tablet to ensure individuals are taking the correct dosage. In this experiment, a UV-Vis spectrophotometer was employed to measure the absorbance of various ASA concentrations, allowing for the calculation of the ASA content in an aspirin tablet.

Experimental

The experimental procedure was conducted as outlined in the lab manual.

Results

Table 1. Mass Data for Acetylsalicylic Acid and Aspirin

The mass of acetylsalicylic acid and the aspirin tablet was determined by weighing the flask and then measuring the flask with acetylsalicylic acid and the aspirin tablet separately. The mass of the compound was calculated by subtracting the mass of the flask and the compound from the mass of the flask. The concentration of acetylsalicylic acid in the stock solution was found by dividing the mass of acetylsalicylic acid by the volume of the volumetric flask, which was 0.25 L.

Table 2. Concentration and Absorbance Data from UV-Vis Spectroscopy

The concentration of the solutions was determined using the equation: C₁V₁=C₂V₂, where C₁V₁ represents the concentration and volume of the stock solution, and C₂V₂ represents the concentration and volume of the diluted solution. The absorbance was measured using the UV-Vis spectrophotometer, and the interpolation value was determined using the LabQuest2.

Calculation of ASA in Tablet

The milligrams of acetylsalicylic acid in a tablet were calculated using the equation derived from Graph 1. The absorbance of the unknown sample (0.181) was used to solve for the concentration (mg/L) of ASA. This concentration was then multiplied by the volume of the diluted solution to determine the mg of acetylsalicylic acid in the diluted solution. Finally, the mass of acetylsalicylic acid in the tablet was found by dividing by the volume of the unknown aspirin tablet stock solution and multiplying by the total volume of the stock solution. The amount of acetylsalicylic acid in a tablet was calculated to be 229 mg.

To determine the percent of acetylsalicylic acid in the tablet, the mass of acetylsalicylic acid was divided by the mass of the tablet recorded in Table 1. The percent of acetylsalicylic acid in a tablet was found to be 60.7%.

Discussion

The experiment resulted in the determination of 229 mg of acetylsalicylic acid in an aspirin tablet, with a calculated percentage of 60.7%. The results align with the data from Table 2. The calculations used to find the ASA content in the tablet were consistent with the units, ensuring the accuracy of the final result.

It is worth noting that the class data exhibited variations in the mass of the aspirin tablet, with a class average of 324 mg, which is in agreement with the theoretical value. However, our data differed by 100 mg, indicating both inaccuracy and imprecision. The percent error was calculated to be -29.5%. The percentage of ASA in the tablet varied widely across the class data, ranging from the 40s to the 110s. Our result of 60.7% deviated by approximately 20% from the class data. The wide range of class data suggests a lack of precision.

Possible sources of error include incomplete quantitative transfers, where some tablet or ASA may have been left in the first Erlenmeyer flask, affecting the accuracy of the stock solution. Such data is crucial in medical contexts to ensure individuals receive the correct medication dosage. Proper dosing of aspirin is essential for individuals with specific medical conditions, such as stroke patients who rely on aspirin for blood thinning. Incorrect dosages could lead to adverse health effects, making research like this vital to prevent prescribing errors.

Conclusion

The experiment successfully determined that an aspirin tablet contains 229 mg of acetylsalicylic acid, representing 60.7% of its composition. The data obtained from Table 1 and Table 2, along with the calibration curve in Graph 1, supported these findings. This information is crucial in the medical field to ensure accurate prescription and dosing of aspirin for various health conditions.