| Sample preparation |
Weigh 0.5 g of the powdered sample and place it in a 10-mL centrifuge tube, then add 2.5 mL of methanol (65%). Sonicate (350 W) the mixture for 30 min. Centrifuge at about 4000 × g for 10 min. Pipette 1 mL of supernatant to 2 mL of water. Pre-condition a solid-phase extraction (SPE) column containing ODS packing (3 mL, 200 mg) with 3 mL of methanol and then followed by 3 mL of methanol (5%). Load the sample solution to the pre-conditioned SPE column. Add 2 mL of methanol (10%) to the column and discard the eluant. Add 0.5 mL of methanol to the column and collect the eluant |
| Mobile phase |
Water, acetonitrile, tetrahydrofuran 6:3:1 (v/v/v) on HPTLC RP-18 F254s plate |
| Derivatization |
Spray with 10% sulfuric acid in ethanol, then heat the plate at 105°C for 2 min |