Exp 8 Lab Report

Exp 8 Lab Report - Quantitative assay of caffeine in...

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Quantitative assay of caffeine in acetaminophen, aspirin, and Goody’s Extra Strength powder using high-performance liquid chromatography (HPLC) Jubilee Ngo, Nora Roberts TA: Christine Huang Section: A00 Chemistry 100A at University of California, San Diego 9500 Gilman Drive, La Jolla, California 92093 3 August 2006 Abstract High-performance liquid chromatography (HPLC) was the technique used in this experiment to determine the percent by mass of caffeine in acetaminophen, aspirin, and Goody’s Extra Strength powder. First, various solutions were prepared, which includes four caffeine standards at different concentrations, acetaminophen, aspirin, and unknown caffeine/Goody’s powder solutions. Next, all of these solutions were analyzed using the HPLC apparatus, which gave their retention times and relative peak areas. The average retention time of the standards is 2.90 ± 0.02 min while the retention times of the acetaminophen is 2.07 min, of the aspirin is 0.98 min, and of the Goody’s powder is 2.85 min. By calculating the relative peak areas and plotting these against the caffeine concentrations of the four standards, interpolation to get the caffeine concentrations of the other three solutions was possible using the resulting trendline, y = 0.01x + 0.0066. Finally, back dilution calculations were performed to obtain the mass and percent by mass of caffeine in the original amounts of the compounds used for analysis. These values are 59.61% (59.91 mg in 0.1005 g) for acetaminophen, 10.81% (11.61 in 0.1074 g) for aspirin, and 2.69% (2.95 in 0.1096 g) for Goody’s powder. The percent by mass of caffeine in Goody’s Extra Strength powder determined in this experiment has a 12.52% relative error compared to the value obtained in a similar experiment reported by Glenda K. Ferguson’s paper, “Quantitative HPLC Analysis of an Analgesic/Caffeine Formulation: Determination of Caffeine.” Result Goody’s Extra Strength Headache medication contains three active ingredients: acetaminophen, aspirin, and caffeine and the background information of these compounds is presented in Table 5 (see the Appendix). Also, Table 6 of the Appendix shows the mass of caffeine solid used for preparation of the standard solutions of caffeine and their actual concentrations in ppm (or mg/L) alongside the intended (theoretical) concentrations (also in ppm). It should be noted that these values are clearly different, which can lead to different results depending on which set of values are used. For this experiment, the actual concentrations are used for increase in accuracy. The following table show the data gathered from the HPLC analysis: retention times and peak areas for all of the solutions in vials 2-8, which include standard caffeine solutions and acetaminophen, aspirin, and unknown caffeine (Goody’s powder) solutions. (On a side note, vial 1 contained the blank solution and its retention time is 0.38 min and peak area is 9430. However, data of this solution is not necessary as it is not used in data analysis.)
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Table 1. Retention times, peak areas, and relative peak areas of all solutions (standards and unknowns)
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Exp 8 Lab Report - Quantitative assay of caffeine in...

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