“…Rat plasma calibration standards were prepared at eight concentration levels by adding 2 μL working standard solution to 50 μL of drug-free rat plasma: 0.5, 1.0, 2.0, 5.0, 10.0, 25.0, 50,0, 100, and 200 ng/mL for CGA and NCGA, 2.5, 5.0, 10.0, 25.0, 50,0, 250, 500, and 1000 ng/mL for CCGA, CA, CA-3-G, and CA-4-G, and 12.5, 25.0, 50.0, 125, 250, 1250, 3750, and 5000 ng/mL for FA, respectively. 5 μL of 5% formic acid was added and vortex-mixed to improve the plasma stability of CGA, CCGA, and NCGA [ 24 , 32 ]. Quality control (QC) samples were prepared at the concentrations of 1.5, 25, and 160 ng/mL for CGA and NCGA, 7.5, 125, and 800 ng/mL for CCGA, CA, CA-3-G, and CA-4-G, and 37.5, 625, and 4000 ng/mL for FA in drug-free rat plasma and then stored at −80 °C until analysis.…”