Determination of caffeine content in Wollega Zones, Ethiopian coffee bean, pulp and leaves by high performance liquid chromatography

Caffeine is a stimulant alkaloid found in aerial parts of many hot beverages, including coffee and tea. Due to its health impact, quantification of caffeine level in coffee is of paramount importance for consumers and traders, as well. Therefore, this study was designed to determine the caffeine content in coffee beverage prepared from coffee beans, pulp and leaves using high performance liquid chromatography coupled with a reverse phase C₈ column and UV-detector. In this study, caffeine sample was extracted from coffee beans, pulp and leaves with boiled distilled water followed by solvent partition with chloroform. The extracted caffeine samples were analyzed alongside caffeine standard solutions over the concentration range of 5-25 μg/mL. For quantitative purposes, the standard caffeine gave an equation of Y=1270560x + 986903 (R² = 0.998) and the retention time of 1.84 ± 0.01 min. In parallel to the standard caffeine solution, peak area of caffeine contents in 20 μL extracted caffeine samples of 2.5 g coffee powder in 100 mL of distilled water coffee beverage were registered. By using the peak area, caffeine concentration in injected sample and its concentration in the total sample solution was calculated. The percentage masses of caffeine (w/w%) in the original coffee samples were 1.30 ± 0.11% for beans, 0.90 ± 0.11% for pulp and 0.65 ± 0.10% for leaves. These results of caffeine contents in coffee beans in Wollega zone show high caffeine contents when compared with previously reported coffee beans (1.01 ± 0.04-1.19 ± 0.02%) of other parts of Ethiopia using UV/Vis. spectrophotometric technique.