Solid‐Phase Extraction Followed by Purification with Tri‐n‐Butylphosphate as a Simple and Useful Rat Plasma Clean‐up Method for HPLC‐UV Determination of Zonampanel Monohydrate (YM872), a Highly Water‐Soluble α‐Amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic Acid Receptor Antagonist

Abstract A high‐performance liquid chromatographic method with ultraviolet detection was developed for the determination of zonampanel monohydrate (YM872), a novel α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid (AMPA) receptor antagonist, in rat plasma. YM872 was extracted via solid‐phase extraction. To remove blank plasma derived endogenous peaks, the extract was further purified by washing with tri‐n‐butyl phosphate and injected onto reversed‐phase HPLC with ultraviolet detection at 333 nm. The precision and accuracy were less than 4.99% and within±7.89%, respectively. The limit of quantification was 10 ng/mL when 1 mL of plasma was used. The usefulness of this method was demonstrated by monitoring plasma concentrations after intravenous administration of YM872 to rats.