Preparation of Sample and Reference Solution for LC-MS/MS

Hugan tablets composed of 4.2 g BR, 4.2 g ASH, 4.2 g IR, 2.2 g SCF, 0.3 g PFS, and 0.2 g MB. First, Hugan tablets, BR, ASH, SCF, IR, PFS, and MB were crushed. Then, 2.0 g of powder was accurately weighed and transferred to a 50-ml triangular flask with plug, in which 25 ml of 70% methanol was added. After 1 h ultrasound-assisted extraction, the extract solution was centrifuged at 12,000 r/min for 10 min and then filtered through a 0.22-μm filter membrane before qualitative analysis. Every single standard solution was prepared by dissolving accurately weighed standards in methanol and stored at 4°C in the dark.