Method Validation for Determination of Caffeine in Sidomulyo Robusta Coffee Beans Using Gas Chromatography-Flame Ionization Detector

Caffeine, an alkaloid compound found in coffee, is widely known for its ability to stimulate the human central nervous system. The caffeine content in Sidomulyo robusta coffee was analyzed using a gas chromatography-flame ionization detector (GC-FID) with ultrasound-assisted extraction as a preparation method using methanol solvent for 21 minutes at 32°C. A TR-1MS column (15m x 0.25 mm ID x 0.25 μm film, non-polar column 100% dimethyl poly-siloxane) was used for the GC analysis. The injector temperature was set at 260°C and the detector at 280°C. The initial oven temperature was set at 100°C, held for 1 minute, then gradually increased by 5°C/minute up to 280°C and held for 2 minutes, with the optimal flow rate condition selected at 1.2 mL/min. This method met all verification criteria and exhibited linearity in the 100–600 mg/L range with a high correlation coefficient of 0.9929, demonstrating its reliability and accuracy in determining caffeine content in coffee samples