Caffeine is a stimulant that most people are familiar with. We usually link it to coffee and carbonated drinks, but it is also found in some foods, such as chocolate. The amount of caffeine varies between coffee brands and different chocolate bars, but through analytical methods we can determine an amount in each. We can then compare the results to find out if there is more caffeine in chocolate or coffee. For this experiment I will give a brief overview of caffeine, theobromine, coffee and chocolate. Through analytical methods, I will demonstrate that there is more caffeine present in a single serving of coffee than in a candy bar. Caffeine is the common name for the chemical compound trimethylxanthine and is produced by many different plants, including coffee beans and cocoa beans. Caffeine stimulates the central nervous system, heart rate, breathing, 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 are found naturally 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). To analyze coffee and chocolate, we will need to separate the components to be studied, known as analytes. Both coffee and chocolate are complex mixtures in which the analytes are caffeine and theobromine. The first step in the analytical process is sample preparation. Sampling is the process of selecting a representative quantity from the initial product. Sample preparation converts that sample into a homogeneous laboratory sample. A homogeneous sample has the same composition everywhere. A straight......middle of paper......is registered. The procedure was repeated again for the same convoluted sample and continued until three chromatograms were recorded. We repeated the steps for each of the remaining standard samples, moving from the most concentrated to the least concentrated, rinsing the syringe a few times with the methanol/water mixture when switching to a caffeine sample of different concentration. Three chromatograms were recorded for each standard (ChemWiki). Measurements of retention time and peak areas were made from the resulting chromatograms. We used the area of ​​all standard peaks to produce a calibration curve. Then, using the calibration curve, we could determine the caffeine concentration in each of the diluted samples. After determining the caffeine concentration in the diluted samples, we could calculate the caffeine concentration in the original sample.