Sample Preparation
STERILE
A representative sample weighing approximately 20 mg was taken from the starting material in the frozen state and transferred into a sterile Eppendorf pipette. Afterward, 200 µL of an aqueous solution of the internal standard in phosphate buffer was added to the sample. The resulting solution was placed in a vortex at +4 °C and centrifuged for 10 min at 1400× 