The extraction efficiency of stimulant drug, namely caffeine, was investigated using a 23 central composite design. values optimum condition were set at 468 ?L 1-dodecanol, 1 piece effervescent tablet, and 22 °C temperature. An enrichment factor calculated as 72 for 80 mL water sample. run time conducted in less than 6 min non-polar C18 column an isocratic mobile phase (methanol: 40:60 (v/v)) c...