Cyclic Acetammetry
The main purpose of this experiment was to utilize the principles of cyclic voltammetry to determine technique accuracy in calculating the actual concentration of an acetaminophen elixir. Five standard solutions of acetaminophen and an acid buffer solution were created and analyzed with a potentiostat to determine the peak anodic voltage and current during the scanning process. Three solutions of Tylenol®—containing acetaminophen—and acid buffer were then created and scanned at the same scan rate as the five standard solutions. Additionally, the most concentrated standard solution was scanned at five different scan rates (between 100 and 500 mV/s) in order to develop a relationship between observed current and scan rate. The Randles-Sevcik
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This plot showed a very high correlation—at 0.9939—between current and concentration, indicating that a direct relationship did, in fact, exist between the two variables. Utilizing the relationship obtained from the five standard solution scans, the experimental concentration of each elixir was determined in mM based on the observed current for each elixir, and it was therefore possible to back-calculate the original elixir acetaminophen concentration given the dilution procedure and density of acetaminophen in the elixir (see C.2 and C.3). The actual concentration of acetaminophen within the Tylenol® was determined from the given data on the product label at 0.2117 M (see C.1). The calculated concentration for each of the solutions was relatively close to this value, at 0.2943, 0.2044, and 0.1917 respectively (see table 2). Had the first elixir solution—at 0.2943 M—been closer to the calculated value, this error would have been significantly less, and the experimental concentration would have been much closer to the actual concentration value. This high deviation (at 39% error from the actual concentration) could have been caused by a few different factors. As experienced within the procedure, incorrect placement or bumping of the potentiostat drastically changed the current observed during the scan. While caution was
This plot showed a very high correlation—at 0.9939—between current and concentration, indicating that a direct relationship did, in fact, exist between the two variables. Utilizing the relationship obtained from the five standard solution scans, the experimental concentration of each elixir was determined in mM based on the observed current for each elixir, and it was therefore possible to back-calculate the original elixir acetaminophen concentration given the dilution procedure and density of acetaminophen in the elixir (see C.2 and C.3). The actual concentration of acetaminophen within the Tylenol® was determined from the given data on the product label at 0.2117 M (see C.1). The calculated concentration for each of the solutions was relatively close to this value, at 0.2943, 0.2044, and 0.1917 respectively (see table 2). Had the first elixir solution—at 0.2943 M—been closer to the calculated value, this error would have been significantly less, and the experimental concentration would have been much closer to the actual concentration value. This high deviation (at 39% error from the actual concentration) could have been caused by a few different factors. As experienced within the procedure, incorrect placement or bumping of the potentiostat drastically changed the current observed during the scan. While caution was