High-performance liquid chromatographic determination of 1,2,3,4-tetrahydroisoquinoline in rat brain with fluorescence detection.

A high-performance liquid chromatographic method for the fluorometric determination of 1,2,3,4-tetrahydroisoquinoline in rat brain is described. 1,2,3,4-Tetrahydroisoquinoline and 4-phenylpiperidine (internal standard) are isolated by liquid-liquid extraction, and then converted into the corresponding fluorescent derivatives with 3,4-dihydro-6,7-dimethoxy-4-methyl-3-oxoquinoxaline-2-carbonyl chloride, a fluorescence derivatization reagent for amines. The derivatives are separated within 60 min on a reversed-phase column, TSK gel ODS-120T, with isocratic elution, and detected fluorometrically. The detection limit of 1,2,3,4-tetrahydroisoquinoline is 1.0 pmol/g in rat brain (S/N = 3).