Analysis of Caffeine

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Caffeine is a stimulant that most people are familiar with. Most typically we connect it with coffee and sodas, but it is also found in certain foods, such as chocolate. The amount of caffeine will vary within coffee brands and in different chocolate bars, but through analytical methods we can determine an amount in each. We can then compare the results to find whether there is more caffeine in chocolate or in coffee. For this experiment I will give a brief overview of caffeine, theobromine, coffee and chocolate. Through analytical methods, I will show that there is more caffeine present in a single serving of coffee than in a chocolate bar. Caffeine is the common name for the chemical compound trimethylxanthine and is produced by many different plants, including coffee beans and cacao beans. Caffeine stimulates the central nervous system, heart rate, respiration, has mood altering properties, and acts as a mild diuretic (About.com). Theobromine is a chemical compound belonging to a class of alkaloid molecules known as methylxanthines. Methylxanthines naturally occur in caffeine. Theobromine affects people similarly to caffeine, but on a much smaller scale. Theobromine is a mild stimulant and a mild diuretic. (About.com). In order to analyze coffee and chocolate, we'll need to separate the components to be studied, known as the the analytes. Both coffee and chocolate are complex mixtures with the analytes being caffeine and theobromine. The first step in the analytical process is sample preparation. Sampling is the process of selecting a representative amount from the initial product. Sample preparation converts that sample into a homogenous laboratory sample. A homogeneous sample has the same composition throughout. A hetero... ... middle of paper ... ...s recorded. The procedure was repeated again for the same contorted sample and continued until we had recorded three chromatograms. We repeated the steps for each of the remaining standard samples, going from the most concentrated to the least concentrated, rinsing the syringe out a few times with the methanol/water mixture when changing to a caffeine sample of different concentration. Three chromatograms were recorded of each standard (ChemWiki). From the resulting chromatograms, measurements of retention time and peak areas were made. We used the area of all standard peaks to produce a calibration curve. Then using the calibration curve, we could determine the concentration of caffeine in each of the diluted samples. After determining the concentration of caffeine in the diluted samples, we could calculate the concentration of caffeine in the original sample.
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