For the system suitability test (SST), a primary standard stock solution with a concentration of 1000 μg/mL was prepared. This was subsequently diluted to obtain a working standard solution with a concentration of 100 μg/mL. The working standard solution was then used as a system suitability standard to assess the precision of the HPLC system. The sample preparation method is described in section 1.3 of the Supporting information (SI).