Caffeine Content of Retail Market Coffee in Portugal

How much caffeine does one ingest when drinking a simple cup of coffee in Portugal? The study presented herein tried to answer this question through the assessment of caffeine content of commercially available espresso coffee samples, both caffeinated and decaffeinated, using a high-performance liquid chromatography assay. Caffeine was rapidly separated from the sample matrix using a RP-18 column (250?×?4 mm i.d., 5 μm). The flow rate was 1.0 mL/min and the mobile phase consisted of water acidified with 5% of orthophosphoric acid/methanol (35:65, v/v). Caffeine was detected directly at 273 nm. The assay was validated for linearity, lower limit of quantification and limit of detection, precision, accuracy, and stability. Seventeen different brands of caffeinated coffee and six of decaffeinated coffee were analyzed. As for capsule coffee, eight caffeinated and two decaffeinated blends were analyzed. The caffeine content of caffeinated coffee varied from 53.8?±?5.9 to 141.3?±?5.3 mg/cup, whereas for caffeinated capsule coffee caffeine concentrations ranged from 45.0?±?5.3 to 60.8?±?6.2 mg/cup. As for decaffeinated coffee, caffeine concentrations ranged from 0.96?±?0.04 to 3.9?±?0.1 mg/cup and for decaffeinated capsule coffee from 0.93?±?0.04 to 1.2?±?0.1 mg/cup.