Sample preparation |
Transfer about 2.5 g of powdered sample, accurately weighed, to a 100 mL round bottom flask fitted with a reflux condenser. Add 25 mL methanol on a water bath for 10 min, cool to room temperature, and decant the supernatant. Repeat until the last extract is colorless. Combine the extracts, filter, concentrate under vacuum, and adjust he volume to 100 mL using methanol. Before injection, pass through a membrane filter of 0.45 µm or finer pore size, discarding the first 5 mL of the filtrate |