Sample preparation Marketed preparation (150 mL) was centrifuged at 6000 rpm for 20 minutes. About 100 mL of supernatant liquid was distilled off and 70 mL of distillate was collected. To the distillate, about 20 mL of internal standard solution of 1-Pentanol (800 mg/L) was added and final volume of made up to 100 mL with distilled water