*2.10. Stability Test*

A homogenized blank tissue sample (5 ± 0.1 g), combined with a low or high concentration of the mixed standard working solution, was used to yield a quality control (QC) sample. QC samples, boasting target drug concentrations of 0.5 μg/kg and 50 μg/kg, were processed in accordance with the method delineated in Section 2.5. The stability of these samples was assessed at different situations: after 30 days of storage at −22 ◦C, after a week's storage at 4 ◦C, after three freeze–thaw cycles, and after exposure to room temperature and light for 24 h. Each concentration was replicated thrice. The actual measured concentration was compared with the theoretical added concentration. The deviation

between each concentration's mean value and the theoretical concentration was calculated, with the relative standard deviation (RSD) aimed to be within 15%.
