apirin13 - Colorimetric Analysis for Detecting Aspirin...

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Colorimetric Analysis for Detecting Aspirin Content A Brand Comparison Date Due: 4/29/05 Group Number: 1WA Section Number: BE 210-102 Group Member Names: Samuel Bernard, Christina Choug, Aditya Humad, Elizabeth MacNeill, Lauren Martz
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BACKGROUND With over 20 billion tablets of aspirin consumed annually in the United States, 1 it is important that the mass of aspirin per tablet match the labeled dosage. This poses the question, how much, if any, variance exists for each brand from the manufacturer’s claimed dosage? Moreover, with so many different brands of aspirin available, does the actual aspirin content in each tablet vary among brands of the same dosage? In the previous experiment, it was found that the determined mass of aspirin in CVS brand tablets varied by less than 5% from the manufacturer’s dosage of 325mg. This experiment expands on these findings by examining three brands as opposed to one. This not only allows for determination of variance from each brand to the manufacturer’s claimed value, but also for comparison of aspirin content across the three brands. The amount of aspirin in a tablet is determined through the use of a spectrophotometric assay. To detect the aspirin, it must first be dissolved in base to produce sodium salicylate, a compound that can be readily identified by the spectrophotometer when complexed with an iron reagent. The dissolution reaction is shown below: 1 Aspirin + 1 NaOH → 1 Sodium Salicylate + 1 Sodium Acetate Once an absorbance value is obtained, the mass of sodium salicylate and the mass of aspirin can be determined through stoichiometric analysis. The spectrophotometer functions by passing a beam of light of a certain wavelength through a sample and determining the transmittance, the ratio of total intensity transmitted to initial intensity of light. The machine then converts this transmittance to absorbance by 2 - log 10 (% transmittance) . Beyond the absorbance range of 0.05 -1.0, the instrumental error becomes significant, and the values are no longer reliable. Therefore, it is important to work within these limits for accurate data. HYPOTHESIS/OBJECTIVE AND AIMS The purpose of this experiment is to determine and compare the mass of aspirin in three different brands of tablets, each with the same reported dosage of 325mg. In pursuit of this objective, a calibration curve for sodium salicylate will be established. Its absorbance readings will then be used to perform a colorimetric analysis to determine the amount of aspirin in a given tablet. To most effectively compare the masses of aspirin between brands, errors by the spectrophotometer and dilution techniques will be minimized. It is hypothesized that there is no statistical difference in the amount of aspirin between the three brands. Additionally, it is hypothesized that the average amount of aspirin determined in each brand of tablet varies no more than 5% from the manufacturer’s claim of 325mg. 1
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apirin13 - Colorimetric Analysis for Detecting Aspirin...

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